CVE-2026-58055
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.
- Published Jun 28, 2026
- CVSS 6.3 medium
- 0.3% chance of exploitation in the next 30 days (EPSS)
- A fix is available
Affected software
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