CVE Catalog

CVE-2026-53341

HighCVSS 7.8
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.12%

2th percentile - higher than 2% of all known CVEs

Summary

A use-after-free (UAF) vulnerability was found in the Linux kernel's may_decode_fh() function in the fhandle mechanism. The issue arises from reading the mount::mnt_ns field without proper locking, allowing a race condition during unmount and namespace deallocation. The fix adds rcu_read_lock() around the mnt_ns access.

Risk Assessment

The risk for organizations is low — the vulnerability requires specific configurations (CONFIG_PREEMPTION or CONFIG_RCU_STRICT_GRACE_PERIOD) and may lead to integer comparison leaks, infinite loops, or kernel crashes. No significant security impact has been identified.

Recommendation

Update the Linux kernel to a version containing the fix (commit in the stable branch). Monitor distributions for the patch and apply it as part of routine maintenance.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh() may_decode_fh() accesses mount::mnt_ns without holding any locks; that means the mount can concurrently be unmounted, and the mnt_namespace can concurrently be freed after an RCU grace period. This race can happens as follows, assuming that the mount point was created by open_tree(..., OPEN_TREE_CLONE): thread 1 thread 2 RCU __do_sys_open_by_handle_at do_handle_open handle_to_path may_decode_fh is_mounted [mount::mnt_ns access] [mount::mnt_ns access] __do_sys_close fput_close_sync __fput dissolve_on_fput umount_tree class_namespace_excl_destructor namespace_unlock free_mnt_ns mnt_ns_tree_remove call_rcu(mnt_ns_release_rcu) mnt_ns_release_rcu mnt_ns_release kfree [mnt_namespace::user_ns access] **UAF** Fix it by taking rcu_read_lock() around the mount::mnt_ns access, like in __prepend_path(). Additionally, document the semantics of mount::mnt_ns, and use WRITE_ONCE() for writers that can race with lockless readers. This bug is unreachable unless one of the following is set: - CONFIG_PREEMPTION - CONFIG_RCU_STRICT_GRACE_PERIOD because it requires an RCU grace period to happen during a syscall without an explicit preemption. This doesn't seem to have interesting security impact; worst-case, it could leak the result of an integer comparison to userspace (from the level check in cap_capable()), cause an endless loop, or crash the kernel by dereferencing an invalid address.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS