CVE-2021-31807: An issue was discovered in Squid before 4.15 and 5.x before 5.0.6.

Security readout for executives and security teams

CVE-2021-31807 can let a remote web server crash or disrupt Squid when Squid processes certain HTTP Range responses. The risky part is operational availability: a common-looking HTTP header can trigger the condition, so it may not look obviously malicious in normal traffic. Exposure is most likely where Squid is deployed as a caching or forwarding proxy and processes HTTP Range responses from external servers. Treat as a practical availability risk for environments that depend on Squid for web access, caching, or security controls. Prioritize patching critical proxy paths, but do not treat it as confirmed exploited based on these sources. Mitigation focus: Upgrade Squid to 4.15, 5.0.6, or later supported releases.; Apply vendor package updates from Debian, Fedora, NetApp, or your platform vendor.; Identify internet-facing or business-critical Squid proxies first..

Prepared

Jun 2, 2026, 19:36 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.