CVE-2026-58055

Name of the Vulnerable Software and Affected Versions nghttp2 nghttpx versions prior to 1.69.0

Description The nghttpx proxy forwards HTTP/1.1 Upgrade requests that contain a Content-Length header and body onto reusable keep-alive backend connections. During this process, it re-adds the Upgrade and Connection headers while passing the Content-Length verbatim. If a backend resolves this ambiguous message in favor of an attacker, it can lead to HTTP request/response smuggling and cross-client response-queue poisoning. There have been reports of increased actor activities targeting this issue.

Recommendations Update nghttp2 nghttpx to version 1.69.0 or later.