CVE-2024-23638: SQUID-2023:11 Denial of Service in Cache Manager

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 60.1% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2024-01-24 · updated 2026-06-17
Weakness: CWE-825

Description

Squid is a caching proxy for the Web. Due to an expired pointer reference bug, Squid prior to version 6.6 is vulnerable to a Denial of Service attack against Cache Manager error responses. This problem allows a trusted client to perform Denial of Service when generating error pages for Client Manager reports. Squid older than 5.0.5 have not been tested and should be assumed to be vulnerable. All Squid-5.x up to and including 5.9 are vulnerable. All Squid-6.x up to and including 6.5 are vulnerable. This bug is fixed by Squid version 6.6. In addition, patches addressing this problem for the stable releases can be found in Squid's patch archives. As a workaround, prevent access to Cache Manager using Squid's main access control: `http_access deny manager`.

Affected products

Squid: from 5.0 through 5.9; from 6.0 before 6.6 — fixed in 6.6

How to fix

Upgrade to a fixed version: Squid 6.6. Check the vendor advisory for mitigations.

References

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