Squid Web Proxy up to 7.4 ICP Request denial of service

Summaryinfo

A vulnerability was found in Squid Web Proxy up to 3.5.28/4.17/5.9/6.14/7.4. It has been declared as problematic. This vulnerability affects unknown code of the component ICP Request Handler. Such manipulation leads to denial of service. This vulnerability is traded as CVE-2026-33526. The attack may be launched remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Squid Web Proxy up to 3.5.28/4.17/5.9/6.14/7.4. It has been rated as problematic. Affected by this issue is some unknown processing of the component ICP Request Handler. The manipulation with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. Impacted is availability. CVE summarizes:

Squid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero `icp_port`). This problem _cannot_ be mitigated by denying ICP queries using `icp_access` rules. Version 7.5 contains a patch.

The advisory is available at seclists.org. This vulnerability is handled as CVE-2026-33526. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

The vulnerability scanner Nessus provides a plugin with the ID 304995 (RHEL 9 : squid (RHSA-2026:6301)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 7.5 eliminates this vulnerability. Applying the patch 8a7d42f9d44befb8fcbbb619505587c8de6a1e91 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (304995) and CERT Bund (WID-SEC-2026-0854). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Affected

• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• Oracle Linux
• RESF Rocky Linux
• Open Source Squid

Productinfo

Type

• Firewall Software

Vendor

• Squid

Name

• Web Proxy

Version

• 3.5.0
• 3.5.1
• 3.5.2
• 3.5.3
• 3.5.4
• 3.5.5
• 3.5.6
• 3.5.7
• 3.5.8
• 3.5.9
• 3.5.10
• 3.5.11
• 3.5.12
• 3.5.13
• 3.5.14
• 3.5.15
• 3.5.16
• 3.5.17
• 3.5.18
• 3.5.19
• 3.5.20
• 3.5.21
• 3.5.22
• 3.5.23
• 3.5.24
• 3.5.25
• 3.5.26
• 3.5.27
• 3.5.28
• 4.0
• 4.1
• 4.2
• 4.3
• 4.4
• 4.5
• 4.6
• 4.7
• 4.8
• 4.9
• 4.10
• 4.11
• 4.12
• 4.13
• 4.14
• 4.15
• 4.16
• 4.17
• 5.0
• 5.1
• 5.2
• 5.3
• 5.4
• 5.5
• 5.6
• 5.7
• 5.8
• 5.9
• 6.0
• 6.1
• 6.2
• 6.3
• 6.4
• 6.5
• 6.6
• 6.7
• 6.8
• 6.9
• 6.10
• 6.11
• 6.12
• 6.13
• 6.14
• 7.0
• 7.1
• 7.2
• 7.3
• 7.4

License

• open-source

Website

• Vendor: http://www.squid-cache.org/

CPE 2.3info

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CPE 2.2info

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Entryinfo

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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