Description
Squid is a caching proxy for the Web. Due to an expired pointer reference bug, Squid prior to version 6.6 is vulnerable to a Denial of Service attack against Cache Manager error responses. This problem allows a trusted client to perform Denial of Service when generating error pages for Client Manager reports. Squid older than 5.0.5 have not been tested and should be assumed to be vulnerable. All Squid-5.x up to and including 5.9 are vulnerable. All Squid-6.x up to and including 6.5 are vulnerable. This bug is fixed by Squid version 6.6. In addition, patches addressing this problem for the stable releases can be found in Squid's patch archives. As a workaround, prevent access to Cache Manager using Squid's main access control: `http_access deny manager`.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| squid-cache | squid | < 6.6 | — |
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 | 6.6-1 | — |
| Debian 13 | squid | 6.6-1 | — |
| Debian 12 | squid | 5.7-2+deb12u1 | DSA-5637-1 |
| Debian 11 | squid | 4.13-10+deb11u3 | DSA-5637-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | squid | 5.7-0ubuntu0.22.04.4 | USN-6728-1 |
| Ubuntu 20.04 LTS | squid | 4.10-1ubuntu1.10 | USN-6728-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 18.04 LTS | squid3 | No fix yet | — |
| Ubuntu Pro 16.04 LTS | squid3 | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9 | squid | 7:5.5-13.el9_4 | RHSA-2024:4861 |
| RHEL 8 | libecap +1 | 1.0.1-2.module+el8.9.0+19703+a1da7223 | RHSA-2024:9644 |
| RHEL 8 | squid | 7:4.15-10.module+el8.10.0+22489+b920747d.3 | RHSA-2024:9644 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 9 | squid | 7:5.5-13.el9_4 | ALSA-2024:4861 |
| AlmaLinux 8 | libecap +1 | 1.0.1-2.module_el8.6.0+2741+01592ae8 | ALSA-2024:9644 |
| AlmaLinux 8 | squid | 7:4.15-10.module_el8.10.0+3916+ed00a4a0.3 | ALSA-2024:9644 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 9 | squid | 7:5.5-13.el9_4 | RLSA-2024:4861 |
| Rocky Linux 8 | libecap | 1.0.1-2.module+el8.9.0+1437+df5ea8f0 | RLSA-2024:9644 |
| Rocky Linux 8 | squid | 7:4.15-10.module+el8.10.0+1758+80ba9f4b | RLSA-2024:9644 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP5 | squid | 5.7-150400.3.23.1 | SUSE-SU-2024:0455-1 |
| SLES 15 SP4 | squid | 5.7-150400.3.23.1 | SUSE-SU-2024:0455-1 |
| SLES 15 SP3 | squid | 4.17-150000.5.49.1 | SUSE-SU-2024:0298-1 |
| SLES 15 SP2 | squid | 4.17-150000.5.49.1 | SUSE-SU-2024:0298-1 |
| SLES 12 SP5 | squid | 4.17-4.41.1 | SUSE-SU-2024:0296-1 |
Show 10 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 SP4 | squid | 5.7-150400.3.23.1 | SUSE-SU-2024:0455-1 |
| SLES for SAP 15 SP3 | squid | 4.17-150000.5.49.1 | SUSE-SU-2024:0298-1 |
| SLES for SAP 15 SP2 | squid | 4.17-150000.5.49.1 | SUSE-SU-2024:0298-1 |
| SLES for SAP 12 SP5 | squid | 4.17-4.41.1 | SUSE-SU-2024:0296-1 |
| SLE HPC 15 SP4 | squid | 5.7-150400.3.23.1 | SUSE-SU-2024:0455-1 |
| SLE HPC 15 SP3 | squid | 4.17-150000.5.49.1 | SUSE-SU-2024:0298-1 |
| SLE HPC 15 SP2 | squid | 4.17-150000.5.49.1 | SUSE-SU-2024:0298-1 |
| SUSE Manager Server 4.3 | squid | 5.7-150400.3.23.1 | SUSE-SU-2024:0455-1 |
| SUSE Manager Proxy 4.3 | squid | 5.7-150400.3.23.1 | SUSE-SU-2024:0455-1 |
| SUSE Enterprise Storage 7.1 | squid | 4.17-150000.5.49.1 | SUSE-SU-2024:0298-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | squid | 6.6-2.1 | openSUSE-SU-2024:13631-1 |
| openSUSE Leap 15.5 | squid | 5.7-150400.3.23.1 | SUSE-SU-2024:0455-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | squid | 7:6.6-1.amzn2023.0.3 | ALAS2023-2024-578 |
| Amazon Linux 2 | squid +2 | 7:3.5.20-17.amzn2.7.17 | ALAS2-2024-2433 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 2 (CBL-Mariner) | squid | No fix yet | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 9 | squid | 7:5.5-13.el9_4 | ELSA-2024-4861 |
| Oracle Linux 8 | libecap +1 | 1.0.1-2.module+el8.9.0+90083+f7556140 | ELSA-2024-9644 |
| Oracle Linux 8 | squid | 7:4.15-10.module+el8.10.0+90442+8ef3f586.3 | ELSA-2024-9644 |
Advisories 17
- WID-SEC-2024-0180 Squid: Schwachstelle ermöglicht Denial of Service BSI CERT-Bund (WID) · Nov 10, 2026
- ALSA-2024:4861 Moderate: squid security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2024:9644 Important: squid:4 security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2024:9644 Red Hat Security Advisory: squid:4 security update Red Hat Security Advisories (RHSA) · Oct 9, 2026
- USN-6728-1 squid vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- RHSA-2024:4861 Red Hat Security Advisory: squid security update Red Hat Security Advisories (RHSA) · Mar 18, 2026
- DSA-5637-1 squid - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2024:4861 Moderate: squid security update Rocky Linux Security Advisories · Feb 5, 2026
- RLSA-2024:9644 Important: squid:4 security update Rocky Linux Security Advisories · Feb 5, 2026
- SUSE-SU-2024:0296-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2024:0298-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2024:0455-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:13631-1 squid-6.6-2.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- ALAS2023-2024-578 Important: squid security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Aug 26, 2025
- ELSA-2024-9644 Important: squid security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 15, 2024
- ELSA-2024-4861 Moderate: squid security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Jul 25, 2024
- ALAS2-2024-2433 Moderate: squid security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Feb 1, 2024
References
- https://github.com/squid-cache/squid/security/advisories/GHSA-j49p-553x-48rx
- https://github.com/squid-cache/squid/commit/290ae202883ac28a48867079c2fb34c40efd382b
- https://github.com/squid-cache/squid/commit/e8118a7381213f5cfcdeb4cec1d2d854bfd261c8
- https://megamansec.github.io/Squid-Security-Audit/stream-assert.html
- http://www.squid-cache.org/Versions/v5/SQUID-2023_11.patch
- http://www.squid-cache.org/Versions/v6/SQUID-2023_11.patch
- https://security.netapp.com/advisory/ntap-20240208-0010/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/7R4KPSO3MQT3KAOZV7LC2GG3CYMCGK7H/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/XWQHRDRHDM5PQTU6BHH4C5KGL37X6TVI/