What is CVE-2026-58055?

CVE-2026-58055 is a medium-severity vulnerability in Nghttp2, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 5.4/10. Published 2026-06-28.

How severe is CVE-2026-58055?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Vulnerability in Nghttp2

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…

Vulnerability class: HTTP Request Smuggling

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N.

Affected products

Nghttp2 — versions 0

Weakness classification (CWE)

CWE-444 — Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling)

References

disclosure@vulncheck.com (exploit, third-party-advisory)
disclosure@vulncheck.com (patch)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-58055?: CVE-2026-58055 is a medium-severity vulnerability in Nghttp2, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 5.4/10. Published 2026-06-28.
How severe is CVE-2026-58055?: Medium severity. CVSS v3 base score is 5.4 out of 10.