CVE-2026-59249
Severity CVSS v4.0:
MEDIUM
Type:
Unavailable / Other
Publication date:
16/07/2026
Last modified:
16/07/2026
Description
Inconsistent interpretation of HTTP requests (HTTP response smuggling) vulnerability in elixir-mint mint allows a malicious HTTP/1 server to desynchronize a strict intermediary and the Mint client on the same pooled connection, enabling response-queue poisoning against subsequent requests that share the connection.<br />
<br />
The Mint.HTTP1.decode_body/5 function in lib/mint/http1.ex parses the chunk-size line of a Transfer-Encoding: chunked response with Integer.parse(data, 16). RFC 7230 defines chunk-size = 1*HEXDIG and forbids any sign prefix, but Integer.parse/2 accepts an optional leading + or -. A chunk-size line of +5 is accepted as a five-byte chunk; lines of +0 and -0 are accepted as the terminating zero-length chunk and end the message body early.<br />
<br />
An RFC-strict intermediary in the response path rejects these forms, so the intermediary and the Mint client disagree on where one response ends and the next begins. On a pooled keep-alive connection, an attacker-influenced origin can inject bytes that the client attributes to the next legitimate response on the same connection, poisoning the response queue and corrupting the responses returned to unrelated in-flight requests.<br />
<br />
This issue affects mint: from 0.1.0 before 1.9.3.
Impact
Base Score 4.0
6.30
Severity 4.0
MEDIUM
References to Advisories, Solutions, and Tools
- https://cna.erlef.org/cves/CVE-2026-59249.html
- https://github.com/elixir-mint/mint/commit/fc7d16538db7e40b56ed489f08683225cb0197fa
- https://github.com/elixir-mint/mint/security/advisories/GHSA-x3x7-96vm-6h2w
- https://osv.dev/vulnerability/EEF-CVE-2026-59249
- https://github.com/elixir-mint/mint/security/advisories/GHSA-x3x7-96vm-6h2w