Denial of Service in Squid ICP request handling
CVE-2026-33526 is a heap use-after-free vulnerability in Squid's handling of ICP (Internet Cache Protocol) traffic. It affects Squid versions prior to 7.5, with advisory material indicating affected branches include 3.x through 7.4. When ICP support is explicitly enabled, a remote attacker can send crafted ICP traffic that triggers the use-after-free condition during ICP request handling, causing the Squid process to crash. The issue is described by the vendor as enabling a reliable and repeatable denial-of-service attack. Although some discussion noted that use-after-free bugs can sometimes have broader consequences, the provided advisory content specifically characterizes this CVE as a denial-of-service issue. The vendor states that version 7.5 contains the patch, and a fixing commit was published for Squid 7.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
icp_port 0 or otherwise ensuring ICP is not enabled. This is the documented workaround. The advisory explicitly states that denying ICP queries with icp_access rules does not mitigate the vulnerability, so access rules alone should not be relied upon.Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
16 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.