What is CVE-2026-54387?

CVE-2026-54387 is a critical-severity vulnerability in Tinyproxy, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 9.1/10. Published 2026-06-17.

How severe is CVE-2026-54387?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Vulnerability in Tinyproxy

CVE-2026-54387

Tinyproxy through 1.11.3, fixed in commit ff45d3b, fails to reconcile conflicting Content-Length and Transfer-Encoding: chunked headers, forwarding both verbatim to the backend while using Content-Length to determine how many request body…

Vulnerability class: HTTP Request Smuggling

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

Affected products

Tinyproxy — versions 0, ff45d3bf0e61d0f8ed97ab379d3047f04eb67521

Weakness classification (CWE)

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

References

disclosure@vulncheck.com (patch)
disclosure@vulncheck.com (technical-description)
disclosure@vulncheck.com (issue-tracking)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-54387?: CVE-2026-54387 is a critical-severity vulnerability in Tinyproxy, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 9.1/10. Published 2026-06-17.
How severe is CVE-2026-54387?: Critical severity. CVSS v3 base score is 9.1 out of 10.