Tinyproxy through 1.11.3, fixed in commit 364cdb6, 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 through 1.11.3, fixed in commit ff45d3b, fails to reconcile conflicting Content-Length and Transfer-Encoding: chunked headers, forwarding both verbatim to the backend while using Content-Length 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 through 1.11.3, fixed in commit 09312a1, 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). A crafted chunk size such as 0x7fffffffffffffff (LONG_MAX) bypasses the existing validation check (chunklen < 0), leading to a signed integer overflow during arithmetic operations (chunklen + 2). This results in incorrect size calculations, causing the proxy to attempt reading an extremely large amount of request-body data and holding worker connections open indefinitely. An attacker can exploit this behavior to exhaust all available worker slots, preventing new connections from being accepted and causing complete service unavailability. Upstream addressed this issue in commit bb7edc4; however, the latest stable release (1.11.3) remains affected at the time of publication.

A use-after-free vulnerability exists in the HTTP Connection Headers parsing in Tinyproxy 1.11.1 and Tinyproxy 1.10.0. A specially crafted HTTP header can trigger reuse of previously freed memory, which leads to memory corruption and could lead to remote code execution. An attacker needs to make an unauthenticated HTTP request to trigger this vulnerability.

tinyproxy HTTP proxy 1.5.0, 1.4.3, and earlier allows remote attackers to execute arbitrary code via memory that is freed twice (double-free).

Buffer overflow in Tinyproxy HTTP proxy 1.3.3 and earlier allows remote attackers to cause a denial of service and possibly execute arbitrary commands via a long connect request.