CVE-2021-3492: Ubuntu linux kernel shiftfs file system double free vulnerability

Security readout for executives and security teams

CVE-2021-3492 is a high-severity Ubuntu Linux kernel flaw in shiftfs. A local, low-privileged attacker could crash affected systems through memory exhaustion or potentially gain higher privileges. The issue matters most on Ubuntu hosts where untrusted users or workloads can run code. Exposure is most likely on Ubuntu systems running affected 5.4 or 5.8 kernel packages that include shiftfs, especially multi-user or workload-hosting systems where low-privileged local code execution is possible. Treat this as a prompt patching item for Ubuntu systems with shared access or untrusted workloads. It is not remotely exploitable based on the supplied CVSS data, but successful local exploitation could lead to full system compromise or denial of service. Mitigation focus: Apply Ubuntu security updates referenced in USN-4917-1.; Reboot systems into the updated kernel after patching.; Prioritize multi-user hosts and systems running untrusted local workloads..

Prepared

May 23, 2026, 08:01 UTC (UTC+00:00)

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