CVE-2026-61642

Description

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.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
squid	26.10 stonking	Not affected
	26.04 LTS resolute	Fixed in 7.7-0ubuntu0.26.04.2
	24.04 LTS noble	Fixed in 6.14-0ubuntu0.24.04.5
	22.04 LTS jammy	Fixed in 5.9-0ubuntu0.22.04.8
	20.04 LTS focal	Fixed in 4.10-1ubuntu1.13+esm3
squid3	26.10 stonking	Not in release
	26.04 LTS resolute	Not in release
	24.04 LTS noble	Not in release
	22.04 LTS jammy	Not in release
	18.04 LTS bionic	Fixed in 3.5.27-1ubuntu1.14+esm6
	16.04 LTS xenial	Fixed in 3.5.12-1ubuntu7.16+esm7

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Notes

mdeslaur

This is fixed in (7.7-0ubuntu0.26.04.1) in resolute-updates, but is not yet in the -security pocket.

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
squid	Upstream: d06f48d

Severity score breakdown

CVSS version: CVSS v3.0

Base score 7.7 · High

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	Low
Privileges required	Low
User interaction	None
Scope	Changed
Confidentiality impact	None
Integrity impact	High
Availability impact	None

Scores

Parameter	Value
Base score	7.7 · High
Exploitability score	-
Impact score	-

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N

References

Related Ubuntu Security Notices (USN)

USN-8998-1
Squid vulnerability
4 November 2026

USN-8941-1
Squid vulnerabilities
20 October 2026