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 (CVSS)
| Base score | 6.3 |
|---|---|
| Severity | Medium |
| Version | CVSS 4.0 |
| Vector | CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:L/SA:N |
| Provided by | CNA |
Weaknesses
- CWE-444 — Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Affected products
| Vendor | Product | Versions |
|---|---|---|
| nghttp2 | nghttp2 | 0 to <=1.69.0 |
References
- https://github.com/bikini/exploitarium/tree/main/nghttp2-nghttpx-upgrade-queue-poison-poc (exploit third-party-advisory)
- https://github.com/nghttp2/nghttp2/commit/ab28105c4a0197da24f8bfc414bc116055249e1e (patch)
- https://www.vulncheck.com/advisories/nghttp2-nghttpx-http-request-response-smuggling-via-upgrade-request-with-content-length (third-party-advisory)
Generated from the official CVE List on 28 Jun 2026 07:01 UTC.