Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. Affected versions of squid are subject to a a Use-After-Free bug which can lead to a Denial of Service attack via collapsed forwarding. All versions of Squid from 3.5 up to and including 5.9 configured with "collapsed_forwarding on" are vulnerable. Configurations with "collapsed_forwarding off" or without a "collapsed_forwarding" directive are not vulnerable. This bug is fixed by Squid version 6.0.1. Users are advised to upgrade. Users unable to upgrade should remove all collapsed_forwarding lines from their squid.conf.
CVSS Details
- CVSS 3.1 Base Score: 8.6
- CVSS 3.1 Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Alpine Linux | — | Upgrade squid | Mar 26, 2024 | Dec 4, 2023 |
| Amazon_linux_2023 | — | Upgrade squidUpgrade squid-debuginfoUpgrade squid-debugsource | Feb 17, 2025 | Dec 5, 2023 |
| Debian | — | Upgrade squid | May 15, 2025 | Dec 4, 2023 |
| Oracle_linux | — | Upgrade squid | Oct 31, 2025 | Dec 5, 2023 |
| Redhat_linux | — | No solution exists | Jul 9, 2025 | Dec 4, 2023 |
| Rocky_linux | — | Upgrade libecap-debugsourceUpgrade libecap-debuginfoUpgrade libecapUpgrade libecap-devel | Mar 20, 2026 | Dec 6, 2023 |
| Ubuntu | — | Upgrade squid | Apr 11, 2024 | Dec 4, 2023 |
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