Vulnerability Description
nghttp2's nghttpx proxy through 1.69.0 forwards an HTTP/1.1 Upgrade request that also carries a Content-Length header and body onto reusable keep-alive backend connections, re-adding the Upgrade and Connection headers while passing Content-Length verbatim. A backend that resolves the resulting ambiguous message in the attacker's favor enables HTTP request/response smuggling and cross-client response-queue poisoning.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/bikini/exploitarium/tree/main/nghttp2-nghttpx-upgrade-queue-p
- https://github.com/nghttp2/nghttp2/commit/ab28105c4a0197da24f8bfc414bc116055249e
- https://www.vulncheck.com/advisories/nghttp2-nghttpx-http-request-response-smugg
FAQ
What is CVE-2026-58055?
CVE-2026-58055 is a vulnerability with a CVSS score of 5.4 (MEDIUM). nghttp2's nghttpx proxy through 1.69.0 forwards an HTTP/1.1 Upgrade request that also carries a Content-Length header and body onto reusable keep-alive backend connections, re-adding the Upgrade and C...
How severe is CVE-2026-58055?
CVE-2026-58055 has been rated MEDIUM with a CVSS base score of 5.4/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-58055?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.