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.

CVSS v3 5.4 MEDIUM

5.4^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.2 / Impact : 2.7

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact LOW

Availability Impact NONE

Scope CHANGED

References

Link	Resource
https://github.com/bikini/exploitarium/tree/main/nghttp2-nghttpx-upgrade-queue-poison-poc	Broken Link
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	Patch Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:nghttp2:nghttp2:*:*:*:*:*:*:*:*

History

30 Jun 2026, 17:41

Type	Values Removed	Values Added
References	~~() https://github.com/bikini/exploitarium/tree/main/nghttp2-nghttpx-upgrade-queue-poison-poc -~~	() https://github.com/bikini/exploitarium/tree/main/nghttp2-nghttpx-upgrade-queue-poison-poc - Broken Link
References	~~() https://github.com/nghttp2/nghttp2/commit/ab28105c4a0197da24f8bfc414bc116055249e1e -~~	() https://github.com/nghttp2/nghttp2/commit/ab28105c4a0197da24f8bfc414bc116055249e1e - Patch
References	~~() https://www.vulncheck.com/advisories/nghttp2-nghttpx-http-request-response-smuggling-via-upgrade-request-with-content-length -~~	() https://www.vulncheck.com/advisories/nghttp2-nghttpx-http-request-response-smuggling-via-upgrade-request-with-content-length - Patch, Third Party Advisory
First Time		Nghttp2 Nghttp2 nghttp2
CPE		cpe:2.3:a:nghttp2:nghttp2::::::::

28 Jun 2026, 02:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-06-28 02:16

Updated : 2026-06-30 17:41

NVD link : CVE-2026-58055

Mitre link : CVE-2026-58055

CVE.ORG link : CVE-2026-58055

JSON object : View

Products Affected

nghttp2

nghttp2

CWE

CWE-444

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

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