CVE-2026-58055
nghttp2 nghttpx - HTTP Request/Response Smuggling via Upgrade Request with Content-Length
CVSS Score
5.4
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-444 |
| Vendor | nghttp2 |
| Product | nghttp2 |
| Published | Jun 28, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None
Affected Versions
nghttp2 / nghttp2
0 ≤ 1.69.0
References
github.com: https://github.com/bikini/exploitarium/tree/main/nghttp2-nghttpx-upgrade-queue-poison-poc github.com: https://github.com/nghttp2/nghttp2/commit/ab28105c4a0197da24f8bfc414bc116055249e1e vulncheck.com: https://www.vulncheck.com/advisories/nghttp2-nghttpx-http-request-response-smuggling-via-upgrade-request-with-content-length
Credits
ashdfrkl