Description
The Squid Software Foundation Squid HTTP Caching Proxy version prior to version 4.0.23 contains a NULL Pointer Dereference vulnerability in HTTP Response X-Forwarded-For header processing that can result in Denial of Service to all clients of the proxy. This attack appear to be exploitable via Remote HTTP server responding with an X-Forwarded-For header to certain types of HTTP request. This vulnerability appears to have been fixed in 4.0.23 and later.
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 | 4.1-1 | — |
| Debian 13 | squid | 4.1-1 | — |
| Debian 12 | squid | 4.1-1 | — |
| Debian 9 | squid3 | 3.5.23-5+deb9u1 | DSA-4122-1 |
| Debian 8 | squid3 | 3.4.8-6+deb8u5 | DSA-4122-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 7 | squid | 2.7.STABLE9-4.1+deb7u3 | DLA-1267-1 |
| Debian 7 | squid3 | 3.1.20-2.2+deb7u8 | DLA-1266-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | squid3 | 3.5.23-5ubuntu2 | — |
| Ubuntu 16.04 LTS | squid3 | 3.5.12-1ubuntu7.5 | USN-3557-1 |
| Ubuntu 14.04 LTS | squid3 | 3.3.8-1ubuntu6.11 | USN-3557-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 7 | squid +2 | 7:3.5.20-15.el7 | RHSA-2020:1068 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP3 | squid | 3.5.21-26.6.1 | SUSE-SU-2018:0636-1 |
| SLES 12 SP2 | squid | 3.5.21-26.6.1 | SUSE-SU-2018:0636-1 |
| SLES 11 SP4 | squid3 | 3.1.23-8.16.37.3.1 | SUSE-SU-2018:0752-1 |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 SP3 | squid | 3.5.21-26.6.1 | SUSE-SU-2018:0636-1 |
| SLES for SAP 12 SP2 | squid | 3.5.21-26.6.1 | SUSE-SU-2018:0636-1 |
| SLES for SAP 11 SP4 | squid3 | 3.1.23-8.16.37.3.1 | SUSE-SU-2018:0752-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | squid | 4.16-1.5 | openSUSE-SU-2024:11403-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | squid | 3.5.27-r2 | — |
| Alpine v3.23 | squid | 3.5.27-r2 | — |
| Alpine v3.22 | squid | 3.5.27-r2 | — |
| Alpine v3.21 | squid | 3.5.27-r2 | — |
| Alpine v3.20 | squid | 3.5.27-r2 | — |
Show 16 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | squid | 3.5.27-r2 | — |
| Alpine v3.18 | squid | 3.5.27-r2 | — |
| Alpine v3.17 | squid | 3.5.27-r2 | — |
| Alpine v3.16 | squid | 3.5.27-r2 | — |
| Alpine v3.15 | squid | 3.5.27-r2 | — |
| Alpine v3.14 | squid | 3.5.27-r2 | — |
| Alpine v3.13 | squid | 3.5.27-r2 | — |
| Alpine v3.12 | squid | 3.5.27-r2 | — |
| Alpine v3.11 | squid | 3.5.27-r2 | — |
| Alpine v3.10 | squid | 3.5.27-r2 | — |
| Alpine v3.9 | squid | 3.5.27-r2 | — |
| Alpine v3.8 | squid | 3.5.27-r2 | — |
| Alpine v3.7 | squid | 3.5.27-r0 | — |
| Alpine v3.6 | squid | 3.5.27-r0 | — |
| Alpine v3.5 | squid | 3.5.27-r0 | — |
| Alpine v3.4 | squid | 3.5.27-r0 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 7 | squid +2 | 7:3.5.20-15.el7 | ELSA-2020-1068 |
Advisories 9
- RHSA-2020:1068 Red Hat Security Advisory: squid security and bug fix update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- DSA-4122-1 squid3 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-1267-1 squid - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-1266-1 squid3 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- USN-3557-1 squid3 vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026
- SUSE-SU-2018:0636-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2018:0752-1 Security update for squid3 SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:11403-1 squid-4.16-1.5 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- ELSA-2020-1068 Moderate: squid security and bug fix update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Apr 6, 2020
References
- USN-3557-1 vendor-advisory
- http://www.squid-cache.org/Versions/v4/changesets/SQUID-2018_2.patch
- DSA-4122 vendor-advisory
- http://www.squid-cache.org/Advisories/SQUID-2018_2.txt
- [debian-lts-announce] 20180202 [SECURITY] [DLA 1266-1] squid3 security update mailing-list
- https://github.com/squid-cache/squid/pull/129/files
- http://www.squid-cache.org/Versions/v3/3.5/changesets/SQUID-2018_2.patch
- [debian-lts-announce] 20180202 [SECURITY] [DLA 1267-1] squid security update mailing-list
- USN-4059-2 vendor-advisory