CVE-2004-0189: Squid

High severity, CVSS 7.5. EPSS: 13.8% chance of exploitation in the next 30 days.

The "%xx" URL decoding function in Squid 2.5STABLE4 and earlier allows remote attackers to bypass url_regex ACLs via a URL with a NULL ("%00") character, which causes Squid to use only a portion of the requested URL when comparing it against the access control lists.

Affected products

• Squid Squid: version 2.0_patch2 only; version 2.1_patch2 only; version 2.3_stable5 only; version 2.4 only; version 2.4_stable7 only; version 2.5_stable3 only; …

Published 2004-03-15. Last modified 2026-06-16.