CVE-2026-58055 — nghttp2 nghttpx - HTTP Request/Response Smuggling via Upgrade Request with Content-Length
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-a…
Published: 2026-06-28 · CVSS: 6.3 · CVSS 4.0
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7