Description
An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Splitting attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This allows any client, including browser scripts, to bypass local security and poison the browser cache and any downstream caches with content from an arbitrary source. Squid uses a string search instead of parsing the Transfer-Encoding header to find chunked encoding. This allows an attacker to hide a second request inside Transfer-Encoding: it is interpreted by Squid as chunked and split out into a second request delivered upstream. Squid will then deliver two distinct responses to the client, corrupting any downstream caches.
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 | 4.13-1 | — |
| Debian 13 | squid | 4.13-1 | — |
| Debian 12 | squid | 4.13-1 | — |
| Debian 10 | squid | 4.6-1+deb10u4 | DSA-4751-1 |
| Debian 9 | squid3 | 3.5.23-5+deb9u5 | DLA-2394-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | squid | 4.10-1ubuntu1.2 | USN-4477-1 |
| Ubuntu 18.04 LTS | squid3 | 3.5.27-1ubuntu1.9 | USN-4551-1 |
| Ubuntu 16.04 LTS | squid3 | 3.5.12-1ubuntu7.15 | USN-4551-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2020:3623 |
| RHEL 8 | squid | 7:4.4-8.module+el8.2.0+7834+b8ecaeef.2 | RHSA-2020:3623 |
| RHEL 7 | squid +2 | 7:3.5.20-17.el7_9.4 | RHSA-2020:4082 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8.1 EUS | libecap +1 | 1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2020:3623 |
| RHEL 8.1 EUS | squid | 7:4.4-8.module+el8.1.0+7837+e38d3ca0.2 | RHSA-2020:3623 |
| RHEL 8.0 E4S | libecap +1 | 1.0.1-2.module+el8.0.0+4045+70edde92 | RHSA-2020:3623 |
| RHEL 8.0 E4S | squid | 7:4.4-5.module+el8.0.0+7838+974c4845.2 | RHSA-2020:3623 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | libecap | 1.0.1-2.module+el8.4.0+404+316a0dc5 | RLSA-2020:3623 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP2 | squid | 4.13-5.23.1 | SUSE-SU-2020:2442-1 |
| SLES 15 SP1 | squid | 4.13-5.23.1 | SUSE-SU-2020:2442-1 |
| SLES 15 | squid | 4.13-5.23.1 | SUSE-SU-2020:2442-1 |
| SLES 12 SP5 | squid | 4.13-4.15.1 | SUSE-SU-2020:2443-1 |
| SLES 12 SP4 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
Show 17 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP3 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
| SLES 12 SP2 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
| SLES 11 SP4 | squid3 | 3.1.23-8.16.37.15.1 | SUSE-SU-2020:14590-1 |
| SLES for SAP 15 | squid | 4.13-5.23.1 | SUSE-SU-2020:2442-1 |
| SLES for SAP 12 SP5 | squid | 4.13-4.15.1 | SUSE-SU-2020:2443-1 |
| SLES for SAP 12 SP4 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
| SLES for SAP 12 SP3 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
| SLES for SAP 12 SP2 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
| SLE HPC 15 | squid | 4.13-5.23.1 | SUSE-SU-2020:2442-1 |
| SUSE OpenStack Cloud Crowbar 9 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
| SUSE OpenStack Cloud Crowbar 8 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
| SUSE OpenStack Cloud 9 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
| SUSE OpenStack Cloud 8 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
| SUSE OpenStack Cloud 7 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | squid3 | 3.1.23-8.16.37.15.1 | SUSE-SU-2020:14590-1 |
| SUSE HPE Helion OpenStack 8 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
| SUSE Enterprise Storage 5 | squid | 3.5.21-26.32.1 | SUSE-SU-2020:2471-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | squid | 4.16-1.5 | openSUSE-SU-2024:11403-1 |
| openSUSE Leap 15.2 | squid | 4.13-lp152.2.6.1 | openSUSE-SU-2020:1369-1 |
| openSUSE Leap 15.1 | squid | 4.13-lp151.2.24.1 | openSUSE-SU-2020:1346-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | squid | 4.13.0-r0 | — |
| Alpine v3.23 | squid | 4.13.0-r0 | — |
| Alpine v3.22 | squid | 4.13.0-r0 | — |
| Alpine v3.21 | squid | 4.13.0-r0 | — |
| Alpine v3.20 | squid | 4.13.0-r0 | — |
Show 11 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | squid | 4.13.0-r0 | — |
| Alpine v3.18 | squid | 4.13.0-r0 | — |
| Alpine v3.17 | squid | 4.13.0-r0 | — |
| Alpine v3.16 | squid | 4.13.0-r0 | — |
| Alpine v3.15 | squid | 4.13.0-r0 | — |
| Alpine v3.14 | squid | 4.13.0-r0 | — |
| Alpine v3.13 | squid | 4.13.0-r0 | — |
| Alpine v3.12 | squid | 4.13-r0 | — |
| Alpine v3.11 | squid | 4.13-r0 | — |
| Alpine v3.10 | squid | 4.13-r0 | — |
| Alpine v3.9 | squid | 4.13-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | squid +2 | 7:3.5.20-17.amzn2.4.1 | ALAS2-2020-1548 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | libecap +1 | 1.0.1-2.module+el8.1.0+5405+03b963f4 | ELSA-2020-3623 |
| Oracle Linux 8 | squid | 7:4.4-8.module+el8.2.0+7778+aff7482f.2 | ELSA-2020-3623 |
| Oracle Linux 7 | squid +2 | 7:3.5.20-17.el7_9.4 | ELSA-2020-4082 |
Advisories 18
- RHSA-2020:4082 Red Hat Security Advisory: squid security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- DSA-4751-1 squid - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2394-1 squid3 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- USN-4551-1 squid3 vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026
- USN-4477-1 squid vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026
- RLSA-2020:3623 Important: squid:4 security update Rocky Linux Security Advisories · Feb 4, 2026
- SUSE-SU-2020:2443-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:2442-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:14590-1 Security update for squid3 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:2471-1 Security update for squid 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
- openSUSE-SU-2020:1346-1 Security update for squid SUSE / openSUSE Security Updates · Feb 4, 2026
- RHSA-2020:3623 Red Hat Security Advisory: squid:4 security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- openSUSE-SU-2020:1369-1 Security update for squid SUSE / openSUSE Security Updates · May 7, 2025
- WID-SEC-2023-2470 Squid: Mehrere Schwachstellen BSI CERT-Bund (WID) · Sep 27, 2023
- ALAS2-2020-1548 Important: squid security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Oct 22, 2020
- ELSA-2020-4082 Important: squid security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Oct 8, 2020
- ELSA-2020-3623 Important: squid:4 security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Sep 4, 2020
References
- https://github.com/squid-cache/squid/security/advisories/GHSA-c7p8-xqhm-49wv
- DSA-4751 vendor-advisory
- USN-4477-1 vendor-advisory
- FEDORA-2020-73af8655eb vendor-advisory
- FEDORA-2020-63f3bd656e vendor-advisory
- openSUSE-SU-2020:1346 vendor-advisory
- openSUSE-SU-2020:1369 vendor-advisory
- FEDORA-2020-6c58bff862 vendor-advisory
- USN-4551-1 vendor-advisory
- [debian-lts-announce] 20201002 [SECURITY] [DLA 2394-1] squid3 security update mailing-list
- https://security.netapp.com/advisory/ntap-20210219-0007/
- https://security.netapp.com/advisory/ntap-20210226-0007/
- https://security.netapp.com/advisory/ntap-20210226-0006/