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Public proof of conceptFix available

CVE-2026-54388

Tinyproxy - HTTP Request Smuggling via Duplicate Content-Length Headers

A public proof of concept exists; no exploitation attested.

  • Published2026-06-17
  • WeaknessCWE-444

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2026-06-1719:59CVE publishedCNA

Versions per branch

Products declared by the CNA1 product

As VulnCheck, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-11-08

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • tinyproxyUbuntu:Pro:22.04:LTSall versions · no fixed version listed
  • tinyproxyUbuntu:Pro:18.04:LTSall versions · no fixed version listed
  • tinyproxyUbuntu:Pro:16.04:LTSall versions · no fixed version listed
  • tinyproxyUbuntu:Pro:14.04:LTSall versions · no fixed version listed
  • tinyproxyUbuntu:26.10all versions · no fixed version listed
  • tinyproxyUbuntu:26.04:LTSall versions · no fixed version listed
  • tinyproxyUbuntu:25.10all versions · no fixed version listed
  • tinyproxyUbuntu:24.04:LTSall versions · no fixed version listed

4 more package ranges on OSV.dev

Full record on NVD

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS 4.0 vector
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:X/V:X/RE:X/U:X
Published
2026-06-17
Last Modified
2026-07-14
NVD status
Deferred
GitHub Advisory
GHSA-p3h9-73g9-x6m3

Frequently asked questions

What is CVE-2026-54388?

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.

Is CVE-2026-54388 actively exploited?

A proof-of-concept exploit exists for CVE-2026-54388, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2026-54388?

CVE-2026-54388 has a CVSS v3 base score of 9.1 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

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