Description
Squid before 4.15 and 5.x before 5.0.6 allows remote servers to cause a denial of service (affecting availability to all clients) via an HTTP response. The issue trigger is a header that can be expected to exist in HTTP traffic without any malicious intent by the server.
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 | 4.13-10 | — |
| Debian 13 | squid | 4.13-10 | — |
| Debian 12 | squid | 4.13-10 | — |
| Debian 10 | squid | 4.6-1+deb10u6 | DSA-4924-1 |
| Debian 9 | squid3 | 3.5.23-5+deb9u7 | DLA-2685-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | squid | 4.10-1ubuntu1.4 | USN-4981-1 |
| Ubuntu 18.04 LTS | squid3 | 3.5.27-1ubuntu1.11 | USN-4981-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 16.04 LTS | squid3 | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2021:4292 |
| RHEL 8 | squid | 7:4.15-1.module+el8.5.0+11469+24c223d9 | RHSA-2021:4292 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | libecap +1 | 1.0.1-2.module_el8.6.0+2741+01592ae8 | ALSA-2021:4292 |
| AlmaLinux 8 | squid | 7:4.15-3.module_el8.6.0+3010+383bc947.1 | ALSA-2021:4292 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | libecap | 1.0.1-2.module+el8.4.0+404+316a0dc5 | RLSA-2021:4292 |
| Rocky Linux 8 | squid | 7:4.15-1.module+el8.5.0+705+218dec94 | RLSA-2021:4292 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP3 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SLES 15 SP2 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SLES 15 SP1 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SLES 15 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SLES 12 SP5 | squid | 4.17-4.24.1 | SUSE-SU-2022:2367-1 |
Show 12 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 SP2 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SLES for SAP 15 SP1 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SLES for SAP 15 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SLES for SAP 12 SP5 | squid | 4.17-4.24.1 | SUSE-SU-2022:2367-1 |
| SLE HPC 15 SP2 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SLE HPC 15 SP1 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SLE HPC 15 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SUSE Manager Server 4.1 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SUSE Manager Retail Branch Server 4.1 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SUSE Manager Proxy 4.1 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SUSE Enterprise Storage 7 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
| SUSE Enterprise Storage 6 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | squid | 5.4.1-2.1 | openSUSE-SU-2024:11929-1 |
| openSUSE Leap 15.3 | squid | 4.17-150000.5.32.1 | SUSE-SU-2022:2553-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | squid | 5.0.6-r0 | — |
| Alpine v3.23 | squid | 5.0.6-r0 | — |
| Alpine v3.22 | squid | 5.0.6-r0 | — |
| Alpine v3.21 | squid | 5.0.6-r0 | — |
| Alpine v3.20 | squid | 5.0.6-r0 | — |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | squid | 5.0.6-r0 | — |
| Alpine v3.18 | squid | 5.0.6-r0 | — |
| Alpine v3.17 | squid | 5.0.6-r0 | — |
| Alpine v3.16 | squid | 5.0.6-r0 | — |
| Alpine v3.15 | squid | 5.0.6-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | squid +2 | 7:3.5.20-17.amzn2.7.2 | ALAS2-2023-1950 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | libecap +1 | 1.0.1-2.module+el8.3.0+7819+eb7d4ef6 | ELSA-2021-4292 |
| Oracle Linux 8 | squid | 7:4.15-1.module+el8.5.0+20327+24c223d9 | ELSA-2021-4292 |
| Oracle Linux 7 | squid +2 | 7:3.5.20-17.0.1.el7_9.6 | ELSA-2021-9465 |
Advisories 13
- ALSA-2021:4292 Moderate: squid:4 security, bug fix, and enhancement update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2021:4292 Red Hat Security Advisory: squid:4 security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Jun 27, 2026
- USN-4981-1 squid, squid3 vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- DSA-4924-1 squid - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2685-1 squid3 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2021:4292 Moderate: squid:4 security, bug fix, and enhancement update Rocky Linux Security Advisories · Feb 4, 2026
- openSUSE-SU-2024:11929-1 squid-5.4.1-2.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2022:2553-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2022:2367-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- WID-SEC-2022-0642 Squid: Schwachstelle ermöglicht Denial of Service BSI CERT-Bund (WID) · Nov 18, 2025
- ALAS2-2023-1950 Moderate: squid security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Feb 22, 2023
- ELSA-2021-4292 Moderate: squid:4 security, bug fix, and enhancement update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 16, 2021
- ELSA-2021-9465 Important: squid security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Sep 24, 2021
References
- https://github.com/squid-cache/squid/security/advisories/GHSA-572g-rvwr-6c7f
- http://www.squid-cache.org/Versions/v5/changesets/squid-5-8af775ed98bfd610f9ce762fe177e01b2675588c.patch
- http://www.squid-cache.org/Versions/v4/changesets/squid-4-1e05a85bd28c22c9ca5d3ac9f5e86d6269ec0a8c.patch
- FEDORA-2021-c0bec55ec7 vendor-advisory
- FEDORA-2021-24af72ff2c vendor-advisory
- [debian-lts-announce] 20210614 [SECURITY] [DLA 2685-1] squid3 security update mailing-list
- [oss-security] 20231011 Squid Caching Proxy Security Audit: 55 Vulnerabilities, 35 0days. mailing-list
- 20231016 Squid Caching Proxy Security Audit: 55 Vulnerabilities, 35 0days. mailing-list