CVE-2026-115877 Twisted: HTTP Request Smuggling in twisted.web via a Bare CR or LF in a Header Value
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-115877?
CVE-2026-115877 is a medium-severity vulnerability in twisted, published on 23 Oct 2026.
Official 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.
Weakness: CWE-444
Which versions are affected by CVE-2026-115877?
2 open source packages ship an affected version, including Twisted and twisted.
| Package | Affected | Fixed in |
|---|---|---|
Twisted PyPI | All versions | 26.10.0rc1 |
twisted PyPI | All versions | 26.10.0rc1 |
How do I fix CVE-2026-115877?
Upgrade Twisted to 26.10.0rc1 or later.
Is CVE-2026-115877 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-115877 exists.
Sources
Also known as AZL-111407, DEBIAN-CVE-2026-115877, ECHO-73bd-6fda-55fe, GHSA-q7qq-6mhp-9rc4, UBUNTU-CVE-2026-115877.