Mount Namespace Vulnerability in Linux Kernel Affecting Users with Locked Covers

CVE-2026-99170

What is CVE-2026-99170?

A vulnerability in the Linux kernel relates to the manipulation of mount namespaces and locked mounts, allowing root users in isolated namespaces to circumvent filesystem protections. By leveraging the copy_tree() functionality, an attacker can successfully discard a locked cover over a file without directly interfering with the underlying filesystem. This flaw can potentially lead to unauthorized access to sensitive file contents while bypassing standard filesystem security measures. Recent commits have addressed this issue by preventing the movement of mount namespace files beneath locked mounts, ensuring greater protection against such exploitation tactics.

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