CVE-2026-33526

A flaw was found in Squid. A remote attacker can exploit a heap Use-After-Free vulnerability when handling ICP (Internet Cache Protocol) traffic. This allows them to perform a reliable and repeatable Denial of Service (DoS) attack, making the Squid service unavailable. This attack is limited to deployments where ICP support is explicitly enabled.

Important: A heap Use-After-Free vulnerability in Squid's ICP handling can lead to a denial of service. This flaw affects Red Hat products where the Squid proxy is configured to explicitly enable Internet Cache Protocol (ICP) support by setting a non-zero icp_port. Deployments with default configurations, where ICP is typically disabled, are not affected.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, disable ICP support in Squid by ensuring that icp_port is set to 0 in the squid.conf configuration file. This will prevent Squid from processing ICP traffic and eliminate the attack vector. After modifying the configuration, the Squid service must be restarted for the changes to take effect.