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 rated as problematic. This issue affects some unknown processing of the component ICP Request Handler. Performing a manipulation results in denial of service. This vulnerability is known as CVE-2026-32748. Remote exploitation of the attack is possible. No exploit is available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as problematic has been found in Squid Web Proxy up to 3.5.28/4.17/5.9/6.14/7.4. This affects an unknown function of the component ICP Request Handler. The manipulation with an unknown input leads to a denial of service vulnerability. CWE is classifying the issue as CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. This is going to have an impact on availability. The summary by CVE is:

Squid is a caching proxy for the Web. Prior to version 7.5, due to premature release of resource during expected lifetime and heap Use-After-Free bugs, 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. This bug is fixed in Squid version 7.5.

It is possible to read the advisory at seclists.org. This vulnerability is uniquely identified as CVE-2026-32748. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

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 703e07d25ca6fa11f52d20bf0bb879e22ab7481b 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). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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