#VU57025 Improper Certificate Validation in Squid - CVE-2021-41611

Vulnerability identifier: #VU57025

Vulnerability risk: Medium

CVSSv4.0: 1.2 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-41611

CWE-ID: CWE-295

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Squid
Server applications / IDS/IPS systems, Firewalls and proxy servers

Vendor: Squid-cache.org

Description

The vulnerability allows a remote attacker to perform a MitM attack.

The vulnerability exists due to improper certificate validation when the TLS server certificate is signed by multiple CAs. A remote attacker can perform a mand-in-the-middle attack against proxy server users.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Squid: 5.0.6 - 5.1

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External links
https://github.com/squid-cache/squid/security/advisories/GHSA-47m4-g3mv-9q5r/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.