CVE-2021-28662

Publication date 27 May 2021

Last updated 25 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

An issue was discovered in Squid 4.x before 4.15 and 5.x before 5.0.6. If a remote server sends a certain response header over HTTP or HTTPS, there is a denial of service. This header can plausibly occur in benign network traffic.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
squid	22.04 LTS jammy	Fixed 4.13-10ubuntu1
	21.10 impish	Fixed 4.13-10ubuntu1
	21.04 hirsute	Fixed 4.13-1ubuntu4.1
	20.10 groovy	Fixed 4.13-1ubuntu2.2
	20.04 LTS focal	Fixed 4.10-1ubuntu1.4
	18.04 LTS bionic	Not in release
	16.04 LTS xenial	Not in release
	14.04 LTS trusty	Not in release
squid3	22.04 LTS jammy	Not in release
	21.10 impish	Not in release
	21.04 hirsute	Not in release
	20.10 groovy	Not in release
	20.04 LTS focal	Not in release
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Not affected
	14.04 LTS trusty	Not in release

Notes

mdeslaur

per upstream, all Squid older than 4.0 are not vulnerable.

Patch details

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

Package	Patch details
squid	Upstream: http://www.squid-cache.org/Versions/v4/changesets/squid-4-b1c37c9e7b30d0efb5e5ccf8200f2a646b9c36f8.patch Upstream: http://www.squid-cache.org/Versions/v6/changesets/squid-6-051824924c709bd6162a378f746fb859454c674e.patch Upstream: 0518249 Upstream: b1c37c9

Severity score breakdown

Parameter	Value
Base score	6.5 · Medium
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	Required
Scope	Unchanged
Confidentiality	None
Integrity impact	None
Availability impact	High
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

References

Related Ubuntu Security Notices (USN)

USN-4981-1
Squid vulnerabilities
3 June 2021