CVE-2026-31842

Tinyproxy through version 1.11.3 fails to reject requests containing multiple Content-Length headers with differing values, forwarding all duplicate headers to the backend while using the first value to determine how many request body bytes to consume. Remote attackers can desynchronize the proxy and backend parser state, allowing injection of arbitrary HTTP requests to the backend to enable cache poisoning, access control bypass, and request hijacking.

Tinyproxy up to version 1.11.3 fails to reconcile conflicting Content-Length and Transfer-Encoding: chunked headers, forwarding both to the backend while using Content-Length to determine request body bytes. Remote attackers can desynchronize proxy and backend parser states, enabling injection of arbitrary HTTP requests to the backend.

Tinyproxy through version 1.11.3 fails to properly validate the Host header during stathost detection, allowing unauthenticated attackers to access the stats page by injecting a matching Host header or bypass detection via port manipulation. Remote attackers can trigger unauthorized access to internal proxy statistics or misroute requests as transparent proxy connections to circumvent access controls.

An integer overflow vulnerability in the HTTP chunked transfer encoding parser in tinyproxy up to and including version 1.11.3 allows an unauthenticated remote attacker to cause a denial of service (DoS). The issue occurs because chunk size values are parsed using strtol without properly validating overflow conditions (e.g., errno == ERANGE).