Description
An issue was discovered in Squid 4.x before 4.15 and 5.x before 5.0.6. If a remote server sends a certain response header over HTTP or HTTPS, there is a denial of service. This header can plausibly occur in benign network traffic.
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 |
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 |
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 | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
| SLES 15 SP2 | squid | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
| SLES 15 SP1 | squid | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
| SLES 15 | squid | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
| SLES 12 SP5 | squid | 4.15-4.18.1 | SUSE-SU-2021:1838-1 |
Show 9 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 SP1 | squid | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
| SLES for SAP 15 | squid | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
| SLES for SAP 12 SP5 | squid | 4.15-4.18.1 | SUSE-SU-2021:1838-1 |
| SLE HPC 15 SP1 | squid | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
| SLE HPC 15 | squid | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
| SUSE Manager Server 4.0 | squid | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
| SUSE Manager Retail Branch Server 4.0 | squid | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
| SUSE Manager Proxy 4.0 | squid | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
| SUSE Enterprise Storage 6 | squid | 4.15-5.26.1 | SUSE-SU-2021:1961-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | squid | 4.16-1.5 | openSUSE-SU-2024:11403-1 |
| openSUSE Leap 15.3 | squid | 4.15-5.26.1 | openSUSE-SU-2021:1961-1 |
| openSUSE Leap 15.2 | squid | 4.15-lp152.2.9.1 | openSUSE-SU-2021:0879-1 |
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 10 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 | — |
| Alpine v3.14 | squid | 5.0.6-r0 | — |
| Alpine v3.13 | squid | 5.0.6-r0 | — |
| Alpine v3.12 | squid | 4.15-r0 | — |
| Alpine v3.11 | squid | 4.15-r0 | — |
| Alpine v3.10 | squid | 4.15-r0 | — |
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 |
Advisories 12
- 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
- RLSA-2021:4292 Moderate: squid:4 security, bug fix, and enhancement update Rocky Linux Security Advisories · Feb 4, 2026
- openSUSE-SU-2024:11403-1 squid-4.16-1.5 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:1961-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:0879-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:1961-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:1838-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- WID-SEC-2022-0672 Squid: Mehrere Schwachstellen ermöglichen Denial of Service BSI CERT-Bund (WID) · Nov 18, 2025
- ELSA-2021-4292 Moderate: squid:4 security, bug fix, and enhancement update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 16, 2021
References
- https://github.com/squid-cache/squid/security/advisories/GHSA-jjq6-mh2h-g39h
- https://github.com/squid-cache/squid/commit/051824924c709bd6162a378f746fb859454c674e
- http://www.squid-cache.org/Versions/v6/changesets/squid-6-051824924c709bd6162a378f746fb859454c674e.patch
- DSA-4924 vendor-advisory
- FEDORA-2021-c0bec55ec7 vendor-advisory
- FEDORA-2021-24af72ff2c vendor-advisory
- [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