What’s Vulnerable › Vulnerabilities

CVE-2026-33526: Squid vulnerable to Denial of Service in ICP Request handling

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 9.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-26 · updated 2026-07-15
• Weakness: CWE-416

Description

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.

Affected products

• Squid: before 7.5 — fixed in 7.5

How to fix

Upgrade to a fixed version: Squid 7.5. Check the vendor advisory for mitigations.

References

• https://github.com/squid-cache/squid/commit/8a7d42f9d44befb8fcbbb619505587c8de6a1e91
• https://github.com/squid-cache/squid/security/advisories/GHSA-hpfx-h48q-gvwg
• http://www.openwall.com/lists/oss-security/2026/03/25/2
• https://access.redhat.com/errata/RHSA-2026:10255
• https://access.redhat.com/errata/RHSA-2026:10256
• https://access.redhat.com/errata/RHSA-2026:10257
• https://access.redhat.com/errata/RHSA-2026:11901
• https://access.redhat.com/errata/RHSA-2026:20564
• https://access.redhat.com/errata/RHSA-2026:20565
• https://access.redhat.com/errata/RHSA-2026:20580
• https://access.redhat.com/errata/RHSA-2026:6301
• https://access.redhat.com/errata/RHSA-2026:8119

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