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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
Low
Partial data modification
Availability
Low
Partial disruption
CVSS Vector v3.1
Weakness Type (CWE)
References 8
https://github.com/sanic-org/sanic/commit/47349d689d65fa1907977ac100e867894aeaf…
security-advisories@github.com
https://github.com/sanic-org/sanic/commit/69a10d3b06babaa9e5f6d1af577364e9e53b6…
security-advisories@github.com
https://github.com/sanic-org/sanic/commit/a332796506c7c588b6930b02a8886e43eb8ea…
security-advisories@github.com
https://github.com/sanic-org/sanic/pull/3164
security-advisories@github.com
https://github.com/sanic-org/sanic/pull/3165
security-advisories@github.com
https://github.com/sanic-org/sanic/releases/tag/v24.12.1
security-advisories@github.com
https://github.com/sanic-org/sanic/releases/tag/v25.12.1
security-advisories@github.com
https://github.com/sanic-org/sanic/security/advisories/GHSA-wmj6-g64g-j7q5
security-advisories@github.com