CVE-2021-41611

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-10-18 · updated 2026-06-17
Weakness: CWE-295

Description

An issue was discovered in Squid 5.0.6 through 5.1.x before 5.2. When validating an origin server or peer certificate, Squid may incorrectly classify certain certificates as trusted. This problem allows a remote server to obtain security trust well improperly. This indication of trust may be passed along to clients, allowing access to unsafe or hijacked services.

Affected products

Fedoraproject Fedora: 35
Squid: from 5.0.6 before 5.2 — fixed in 5.2

How to fix

Upgrade to a fixed version: Squid 5.2. Check the vendor advisory for mitigations.

References

http://www.openwall.com/lists/oss-security/2021/12/23/2
http://www.squid-cache.org/Versions/v6/changesets/squid-6-43d6b5c81b88ec2256b430c69a872a1e4f324e4a.patch
https://github.com/squid-cache/squid/security/advisories/GHSA-47m4-g3mv-9q5r
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CWQ2WKDWTSO47S3F6XJJ6HGG2ULWEAE4/
http://www.openwall.com/lists/oss-security/2021/12/23/2
http://www.squid-cache.org/Versions/v6/changesets/squid-6-43d6b5c81b88ec2256b430c69a872a1e4f324e4a.patch
https://github.com/squid-cache/squid/security/advisories/GHSA-47m4-g3mv-9q5r
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CWQ2WKDWTSO47S3F6XJJ6HGG2ULWEAE4/

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