Threat Advisory

Sanic Flaw Allows Hidden Second Request Execution Through Chunked Trailer Smuggling

Threat: Vulnerability
Targeted Region: Global
Targeted Sector: Technology & IT
Criticality: Medium
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EXECUTIVE SUMMARY:

A medium-severity vulnerability in Sanic allows hidden second request execution through chunked trailer smuggling. The issue is a request-boundary integrity failure in Sanic's HTTP/1.1 parser, which does not fully consume the `trailer-part` after the terminating `0 ` chunk, allowing attacker-controlled bytes to be interpreted as the start of a new HTTP request on the same keep-alive connection. This can lead to unintended execution of hidden requests, potentially resulting in unauthorized access or data modification. The affected versions are prior to 24.12.1 and >=25.12.0, <25.12.1. Remediation involves ensuring that Sanic fully consumes the `trailer-part` after the terminating `0 ` chunk, rejecting any request with bytes after the final empty line before reusing the connection buffer.

RECOMMENDATION:

We recommend you to update Sanic to version 24.12.1 or 25.12.1.[/subscribe_to_unlock_form]

EXECUTIVE SUMMARY:

A medium-severity vulnerability in Sanic allows hidden second request execution through chunked trailer smuggling. The issue is a request-boundary integrity failure in Sanic's HTTP/1.1 parser, which does not fully consume the `trailer-part` after the terminating `0 ` chunk, allowing attacker-controlled bytes to be interpreted as the start of a new HTTP request on the same keep-alive connection. This can lead to unintended execution of hidden requests, potentially resulting in unauthorized access or data modification. The affected versions are prior to 24.12.1 and >=25.12.0, <25.12.1. Remediation involves ensuring that Sanic fully consumes the `trailer-part` after the terminating `0 ` chunk, rejecting any request with bytes after the final empty line before reusing the connection buffer.

RECOMMENDATION:

We recommend you to update Sanic to version 24.12.1 or 25.12.1.[emaillocker id="1283"]

REFERENCES:

The following reports contain further technical details:

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