Description
An issue was discovered in Squid through 4.7. When Squid is run as root, it spawns its child processes as a lesser user, by default the user nobody. This is done via the leave_suid call. leave_suid leaves the Saved UID as 0. This makes it trivial for an attacker who has compromised the child process to escalate their privileges back to root.
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 | No fix yet | — |
| Debian 13 | squid | No fix yet | — |
| Debian 12 | squid | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | squid | No fix yet | — |
| Ubuntu 26.04 LTS | squid | No fix yet | — |
| Ubuntu 25.10 | squid | No fix yet | — |
| Ubuntu 24.04 LTS | squid | No fix yet | — |
| Ubuntu 22.04 LTS | squid | No fix yet | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | squid | No fix yet | — |
| Ubuntu Pro 18.04 LTS | squid3 | No fix yet | — |
| Ubuntu Pro 16.04 LTS | squid3 | No fix yet | — |