CVE-2026-58055 – nghttp2 nghttpx – HTTP Request/Response Smuggling via Upgrade Request with Content-Length

CVE ID :CVE-2026-58055

Published : June 28, 2026, 1:32 a.m. | 2 hours, 12 minutes ago

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.

Severity: 6.3 | MEDIUM

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