---
id: CVE-2026-54388
title: Tinyproxy - HTTP Request Smuggling via Duplicate Content-Length Headers
summary: >-
  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 ma…
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'
cvssSource: cna
cwe:
  - CWE-444
vendor: tinyproxy
product: tinyproxy
affected:
  - tinyproxy <= 1.11.3
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-06-18T15:33:31.245200Z'
exploitAvailable: true
published: '2026-06-17'
updated: '2026-11-08'
sourceUpdated: '2026-11-08T14:05:20.429Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-54388'
references:
  - url: 'https://github.com/tinyproxy/tinyproxy/issues/609'
    label: Researcher Pull Request
  - url: 'https://github.com/tinyproxy/tinyproxy/pull/610'
    label: Maintainer Pull Request
  - url: >-
      https://github.com/tinyproxy/tinyproxy/commit/364cdb67e0ea00a8e4a7037e2693e0711e816adb
    label: Patch Commit
  - url: >-
      https://www.vulncheck.com/advisories/tinyproxy-http-request-smuggling-via-duplicate-content-length-headers
tags:
  - cve.org
  - exploit-available
epss: 0.00439
epssPercentile: 0.38377
ingestedAt: '2026-11-08T14:51:22.375Z'
---

## Overview

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.

## Affected

- `tinyproxy <= 1.11.3`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.