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.
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Squid | Squid-cache | 3.5 (including) | 5.9 (including) |
| Red Hat Enterprise Linux 8 | RedHat | squid:4-8090020231130092412.a75119d5 | * |
| Red Hat Enterprise Linux 9 | RedHat | squid-7:5.5-6.el9_3.2 | * |
| Squid | Ubuntu | bionic | * |
| Squid | Ubuntu | esm-infra/focal | * |
| Squid | Ubuntu | focal | * |
| Squid | Ubuntu | jammy | * |
| Squid | Ubuntu | lunar | * |
| Squid | Ubuntu | trusty | * |
| Squid | Ubuntu | upstream | * |
| Squid | Ubuntu | xenial | * |
| Squid3 | Ubuntu | bionic | * |
| Squid3 | Ubuntu | esm-infra/bionic | * |
| Squid3 | Ubuntu | esm-infra/xenial | * |
| Squid3 | Ubuntu | trusty | * |
| Squid3 | Ubuntu | xenial | * |