Description
Sanic is an opensource python web server/framework. In version 25.12.0, Sanic's core HTTP/1.1 chunked-body handling does not fully consume the trailer-part after the terminating zero chunk before reusing the keep-alive connection buffer. A remote unauthenticated client can place attacker-controlled bytes in that trailer region, causing Sanic to parse and route them as a hidden second request after the outer request. This breaks HTTP request-boundary integrity and can provide a request-smuggling primitive when Sanic is deployed behind intermediaries. This issue is fixed in version 25.12.1.
References8
- github.com/sanic-org/sanic/commit/47349d689d65fa1907977ac100e86…
- github.com/sanic-org/sanic/commit/69a10d3b06babaa9e5f6d1af57736…
- github.com/sanic-org/sanic/commit/a332796506c7c588b6930b02a8886…
- github.com/sanic-org/sanic/pull/3164
- github.com/sanic-org/sanic/pull/3165
- github.com/sanic-org/sanic/releases/tag/v24.12.1
- github.com/sanic-org/sanic/releases/tag/v25.12.1
- github.com/sanic-org/sanic/security/advisories/GHSA-wmj6-g64g-j…
Metrics
- CVSS 3.1
-
6.5
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L - EPSS — exploit probability
- 1% percentile: 44 · 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.