Out-of-Bounds Read in Squid ICP Message Handling
CVE-2026-33515 is an out-of-bounds read vulnerability in Squid's handling of ICP (Internet Cache Protocol) traffic, caused by improper input validation. When a vulnerable Squid instance processes malformed or invalid ICP requests, it may read memory beyond the intended bounds and include small portions of process memory in error responses. According to the provided content, the issue affects Squid versions 3.0 through 7.4, specifically including 3.x through 3.5.28, 4.x through 4.17, 5.x through 5.9, 6.x through 6.14, and 7.x through 7.4. The flaw is only reachable on deployments where ICP support is explicitly enabled via a non-zero icp_port. The issue was fixed in Squid 7.5.
Are you exposed to this one?
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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 to disable it. The provided content states that icp_access rules do not mitigate this vulnerability, so filtering ICP queries with access rules should not be relied upon as a workaround.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
8 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.