CVE-2026-33526: Squid vulnerable to Denial of Service in ICP Request handling
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 icpport). This problem cannot be mitigated by denying ICP queries using icpaccess rules. Version 7.5 contains a patch.
Other sources
Squid vulnerable to Denial of Service in ICP Request handling
— Microsoft
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-33526?
CVE-2026-33526 has a high severity level due to its potential for allowing Denial of Service attacks.
How do I fix CVE-2026-33526?
To fix CVE-2026-33526, upgrade to Squid version 7.5 or later.
What kind of attack does CVE-2026-33526 enable?
CVE-2026-33526 enables a remote attacker to conduct Denial of Service attacks through improper handling of ICP requests.
Which versions of Squid are affected by CVE-2026-33526?
CVE-2026-33526 affects versions of Squid prior to version 7.5.
How can I determine if my system is vulnerable to CVE-2026-33526?
You can determine if your system is vulnerable to CVE-2026-33526 by checking if you are using a version of Squid lower than 7.5.