Published April 7, 2026 · Updated April 7, 2026
CVE-2026-31842 is a high-severity vulnerability in Tinyproxy versions up to 1.11.3, stemming from improper handling of the Transfer-Encoding header due to case sensitivity in comparisons. An unauthenticated attacker can exploit this flaw by sending a request with "Chunked" instead of "chunked," leading Tinyproxy to misinterpret the request, causing connections to backend servers, like Node.js or Nginx, to hang indefinitely. Security teams should upgrade Tinyproxy to the latest version to mitigate this vulnerability and review logging and filtering configurations to ensure proper request handling.
Tinyproxy through 1.11.3 is vulnerable to HTTP request parsing desynchronization due to a case-sensitive comparison of the Transfer-Encoding header in src/reqs.c. The is_chunked_transfer() function uses strcmp() to compare the header value against "chunked", even though RFC 7230 specifies that transfer-coding names are case-insensitive. By sending a request with Transfer-Encoding: Chunked, an unauthenticated remote attacker can cause Tinyproxy to misinterpret the request as having no body. In this state, Tinyproxy sets content_length.client to -1, skips pull_client_data_chunked(), forwards request headers upstream, and transitions into relay_connection() raw TCP forwarding while unread body data remains buffered. This leads to inconsistent request state between Tinyproxy and backend servers. RFC-compliant backends (e.g., Node.js, Nginx) will continue waiting for chunked body data, causing connections to hang indefinitely. This behavior enables application-level denial of service through backend worker exhaustion. Additionally, in deployments where Tinyproxy is used for request-body inspection, filtering, or security enforcement, the unread body may be forwarded without proper inspection, resulting in potential security control bypass.
CVE-2026-31842 is a high-severity vulnerability in Tinyproxy (versions up to 1.11.3) due to case-sensitive HTTP request parsing. Exploitation may cause backend server hangs and bypass security controls. Update Tinyproxy immediately.