Description
An issue was discovered in Squid through 4.7. When handling requests from users, Squid checks its rules to see if the request should be denied. Squid by default comes with rules to block access to the Cache Manager, which serves detailed server information meant for the maintainer. This rule is implemented via url_regex. The handler for url_regex rules URL decodes an incoming request. This allows an attacker to encode their URL to bypass the url_regex check, and gain access to the blocked resource.
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 | 4.8-1 | — |
| Debian 13 | squid | 4.8-1 | — |
| Debian 12 | squid | 4.8-1 | — |
| Debian 10 | squid | 4.6-1+deb10u2 | DSA-4682-1 |
| Debian 9 | squid3 | 3.5.23-5+deb9u2 | DLA-2278-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | squid3 | 3.5.27-1ubuntu1.7 | USN-4446-1 |
| Ubuntu 16.04 LTS | squid3 | 3.5.12-1ubuntu7.12 | USN-4446-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2020:4743 |
| RHEL 8 | squid | 7:4.11-3.module+el8.3.0+7851+7808b5f9 | RHSA-2020:4743 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | libecap +1 | 1.0.1-2.module_el8.6.0+2741+01592ae8 | ALSA-2020:4743 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | libecap | 1.0.1-2.module+el8.4.0+404+316a0dc5 | RLSA-2020:4743 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP4 | squid | 3.5.21-26.23.1 | SUSE-SU-2020:1227-1 |
| SLES 12 SP3 | squid | 3.5.21-26.23.1 | SUSE-SU-2020:1227-1 |
| SLES 12 SP2 | squid | 3.5.21-26.23.1 | SUSE-SU-2020:1227-1 |
| SLES 11 SP4 | squid3 | 3.1.23-8.16.37.12.1 | SUSE-SU-2020:14460-1 |
Show 9 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 SP4 | squid | 3.5.21-26.23.1 | SUSE-SU-2020:1227-1 |
| SLES for SAP 12 SP3 | squid | 3.5.21-26.23.1 | SUSE-SU-2020:1227-1 |
| SLES for SAP 12 SP2 | squid | 3.5.21-26.23.1 | SUSE-SU-2020:1227-1 |
| SUSE OpenStack Cloud Crowbar 8 | squid | 3.5.21-26.23.1 | SUSE-SU-2020:1227-1 |
| SUSE OpenStack Cloud 8 | squid | 3.5.21-26.23.1 | SUSE-SU-2020:1227-1 |
| SUSE OpenStack Cloud 7 | squid | 3.5.21-26.23.1 | SUSE-SU-2020:1227-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | squid3 | 3.1.23-8.16.37.12.1 | SUSE-SU-2020:14460-1 |
| SUSE HPE Helion OpenStack 8 | squid | 3.5.21-26.23.1 | SUSE-SU-2020:1227-1 |
| SUSE Enterprise Storage 5 | squid | 3.5.21-26.23.1 | SUSE-SU-2020:1227-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | squid +2 | 7:3.5.20-17.amzn2.7.10 | ALAS2-2023-2318 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | libecap +1 | 1.0.1-2.module+el8.3.0+7819+eb7d4ef6 | ELSA-2020-4743 |
| Oracle Linux 8 | squid | 7:4.11-3.module+el8.3.0+7819+eb7d4ef6 | ELSA-2020-4743 |
| Oracle Linux 7 | squid | 7:4.11-3.0.1.el7 | ELSA-2022-22254 |
Advisories 12
- ALSA-2020:4743 Moderate: squid:4 security, bug fix, and enhancement update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2020:4743 Red Hat Security Advisory: squid:4 security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Jul 4, 2026
- DSA-4682-1 squid - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2278-1 squid3 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- USN-4446-1 squid3 vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026
- RLSA-2020:4743 Moderate: squid:4 security, bug fix, and enhancement update Rocky Linux Security Advisories · Feb 4, 2026
- SUSE-SU-2020:1227-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:14460-1 Security update for squid3 SUSE / openSUSE Security Updates · May 2, 2025
- ALAS2-2023-2318 Critical: squid security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Nov 6, 2023
- WID-SEC-2022-1594 Squid: Mehrere Schwachstellen BSI CERT-Bund (WID) · Oct 26, 2023
- ELSA-2022-22254 Important: squid security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Oct 3, 2022
- ELSA-2020-4743 Moderate: squid:4 security, bug fix, and enhancement update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 10, 2020