---
id: CVE-2026-61642
title: Squid is a caching proxy for the Web
summary: >-
  Squid is a caching proxy for the Web. From 3.3.0.1 to before 7.6, due to an
  improper enforcement of behavioral workflow bug, Squid is vulnerable to a
  Request Smuggling attack against HTTP/1.1 Transfer-Encoding. HTTP header
  parsing (`src/…
severity: high
cvss: 7.7
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N'
cwe:
  - CWE-444
published: '2026-10-13'
updated: '2026-10-13'
sourceUpdated: '2026-10-13T18:17:25.467'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-61642'
references:
  - url: >-
      https://github.com/squid-cache/squid/commit/d06f48de8b8cc9a378cb91ecfe8e89b6e81696d2
    label: security-advisories@github.com
  - url: >-
      https://github.com/squid-cache/squid/commit/d808a7c825a70275113790471135c9c4d547ee51
    label: security-advisories@github.com
  - url: 'https://github.com/squid-cache/squid/pull/2427'
    label: security-advisories@github.com
  - url: 'https://github.com/squid-cache/squid/pull/2431'
    label: security-advisories@github.com
  - url: 'https://github.com/squid-cache/squid/releases/tag/SQUID_7_6'
    label: security-advisories@github.com
  - url: >-
      https://github.com/squid-cache/squid/security/advisories/GHSA-537g-4gfh-w7m6
    label: security-advisories@github.com
tags:
  - nvd
ingestedAt: '2026-10-13T17:38:53.197Z'
---

## Overview

Squid is a caching proxy for the Web. From 3.3.0.1 to before 7.6, due to an improper enforcement of behavioral workflow bug, Squid is vulnerable to a Request Smuggling attack against HTTP/1.1 Transfer-Encoding. HTTP header parsing (`src/HttpHeader.cc`) accepted the bare` Transfer-Encoding:` identity form, which the HTTP specification prohibits because any transfer coding must be wrapped within chunked encoding. This problem allows a trusted client to perform an HTTP Request Smuggling attack when HTTP/1.1 is used, bypassing security mechanisms that may be in place between attacker and Squid. When there is an HTTP cache operating prior to the affected Squid, this Request Smuggling attack also allows the attacker to poison that web cache and store arbitrary malicious content at any URL for delivery to other clients' future requests. This issue is fixed in version 7.6.

## Remediation

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