Description
Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 26.10.0rc1, twisted.web.http.HTTPChannel.headerReceived rejects a NUL byte in an HTTP header value but accepts a bare carriage return or bare line feed. Because Twisted splits header lines only on CRLF, a hidden Content-Length header can remain folded into another value while a lenient front end treats the bare character as a line terminator. The resulting framing disagreement can smuggle a following request past front-end access controls, poison a shared connection or cache, and expose a later client to the wrong response. This issue is an incomplete-fix residual of earlier Twisted request-smuggling protections. This issue is fixed in version 26.10.0rc1.
References6
- github.com/twisted/twisted/commit/022b6f7feb5980166c71f54e2c0d8…
- github.com/twisted/twisted/commit/1616f702d36eda8990a5a5b22ad70…
- github.com/twisted/twisted/pull/12755
- github.com/twisted/twisted/releases/tag/twisted-26.10.0rc1
- github.com/twisted/twisted/security/advisories/GHSA-q7qq-6mhp-9…
- github.com/twisted/twisted/security/advisories/GHSA-q7qq-6mhp-9…
Metrics
- CVSS 3.1
-
5.4
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N - EPSS — exploit probability
- 0% percentile: 17 · as of 8 November 2026
- CWE
- CWE-444
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.