Description
Squid 2.5, when processing the configuration file, parses empty Access Control Lists (ACLs), including proxy_auth ACLs without defined auth schemes, in a way that effectively removes arguments, which could allow remote attackers to bypass intended ACLs if the administrator ignores the parser warnings.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | squid | 2.5.7-7 | — |
| Debian 13 | squid | 2.5.7-7 | — |
| Debian 12 | squid | 2.5.7-7 | — |
| Debian 3.0 | squid | 2.4.6-2woody6 | DSA-667-1 |
Advisories 1
- DSA-667-1 squid - several Debian Security (DSA / DLA) · Mar 9, 2026
References
- CLA-2005:923 vendor-advisory
- http://www.squid-cache.org/Versions/v2/2.5/bugs/#squid-2.5.STABLE7-empty_acls
- 20050221 [USN-84-1] Squid vulnerabilities mailing-list
- http://www.squid-cache.org/Versions/v2/2.5/bugs/squid-2.5.STABLE7-empty_acls.patch
- FLSA-2006:152809 vendor-advisory
- http://www.squid-cache.org/bugs/show_bug.cgi?id=1166
- DSA-667 vendor-advisory
- VU#260421 third-party-advisory