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Vulnerability record · CVE-2026-54388 · published 17 June 2026

CVE-2026-54388: HTTP request smuggling vulnerability

Tinyproxy through 1.11.3, fixed in commit 364cdb6, fails to reject requests containing multiple Content-Length headers with differing values, forwarding all duplicate headers to the backend while using the first value to determine how many request body bytes to consume. Remote attackers can desynchronize the proxy and backend parser state, allowing injection of arbitrary HTTP requests to the backend to enable cache poisoning, access control bypass, and request hijacking.

9.3 CVSS 4.0 Critical EPSS 0.68% · top 49.8% CWE-444 · HTTP request smuggling Deferred
9.3CVSS 4.0 base score
0.68%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
5References
14 Jul 2026Last modified by NVD

Description

Tinyproxy through 1.11.3, fixed in commit 364cdb6, fails to reject requests containing multiple Content-Length headers with differing values, forwarding all duplicate headers to the backend while using the first value to determine how many request body bytes to consume. Remote attackers can desynchronize the proxy and backend parser state, allowing injection of arbitrary HTTP requests to the backend to enable cache poisoning, access control bypass, and request hijacking.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/tinyproxy/tinyproxy/commit/364cdb67e0ea00a8e4a7037e2693e0711e816adb
https://github.com/tinyproxy/tinyproxy/issues/609
https://github.com/tinyproxy/tinyproxy/pull/610
https://www.vulncheck.com/advisories/tinyproxy-http-request-smuggling-via-duplicate-content-length-headers
https://github.com/tinyproxy/tinyproxy/issues/609

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Source: NIST National Vulnerability Database (record CVE-2026-54388), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.