CVE-2026-33526criticalCWE-416CWE-825CWE-826

CVE-2026-33526: critical vulnerability in squid-cache squid

Squid vulnerable to Denial of Service in ICP Request handling

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28Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 9.2epss 9.1%
In short

Squid proxy versions before 7.5 have a memory bug that crashes the service when receiving certain ICP protocol messages, allowing attackers to knock the proxy offline. This affects only deployments that have ICP enabled.

Technical detail

A use-after-free vulnerability (CWE-416) in ICP request handling allows remote attackers to trigger a denial of service by sending crafted ICP packets to the configured icp_port. The vulnerability cannot be mitigated with icp_access rules and requires Squid 7.5+ or disabling ICP entirely.

Summary generated and translated by AI from the official 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.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
Affected products
squid-cache · squid
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