Description
Incorrect HTTP Request header comparison in Squid HTTP Proxy 3.5.0.1 through 3.5.22, and 4.0.1 through 4.0.16 results in Collapsed Forwarding feature mistakenly identifying some private responses as being suitable for delivery to multiple clients.
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.
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 16.04 LTS | squid3 | 3.5.12-1ubuntu7.3 | USN-3192-1 |
| Ubuntu 14.04 LTS | squid3 | 3.3.8-1ubuntu6.9 | USN-3192-1 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP2 | squid | 3.5.21-25.1 | SUSE-SU-2017:0128-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 SP2 | squid | 3.5.21-25.1 | SUSE-SU-2017:0128-1 |
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 v3.3 | squid | 3.5.23-r0 | — |
| Alpine v3.2 | squid | 3.5.23-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | squid +2 | 7:3.5.20-17.amzn2.7.6 | ALAS2-2023-2066 |
Advisories 5
- USN-3192-1 squid3 vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026
- SUSE-SU-2017:0128-1 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
- WID-SEC-2023-1362 Squid: Mehrere Schwachstellen ermöglichen Offenlegung von Informationen BSI CERT-Bund (WID) · Jun 8, 2023
- ALAS2-2023-2066 Important: squid security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Jun 1, 2023