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Linux KernelOperating system · Linux

CVE-2026-53341

HIGH · 7.8 CVSS v3.1 Published 2026-07-01
Fix available
A fix is available. Upgrade to 6.12.95 / 6.18.36 or later.
See remediation →
80/100
Remediation priority · High
Zero-click 7 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A Use-After-Free (UAF) vulnerability in the Linux kernel's fhandle subsystem where may_decode_fh() accesses mount::mnt_ns without holding RCU locks, allowing concurrent unmount operations to free the mnt_namespace after an RCU grace period, leading to a UAF when the freed memory is accessed.

MitigationApply the kernel patch adding rcu_read_lock() around mount::mnt_ns access and use WRITE_ONCE() for writers; ensure systems with CONFIG_PREEMPTION or CONFIG_RCU_STRICT_GRACE_PERIOD are prioritized for patching.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 6.11, < 6.12.95>= 6.13, < 6.18.36>= 6.19, < 7.0.13= 7.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify kernel version
    Run 'uname -r' or check /proc/version to get the running kernel version
    Affected if The kernel version is within the affected range (no specific range provided; compare to upstream fix commits if available)
  2. Check if fhandle subsystem is accessible
    Verify if the kernel has CONFIG_EXPORTFS_BLOCK_OPS or CONFIG_EXPORTFS enabled, and check if the kernel supports open_by_handle_at syscall (present in kernel 2.6.39+)
    Affected if The fhandle subsystem and open_by_handle_at syscall are available in the kernel
  3. Monitor for open_by_handle_at usage
    Use 'auditctl -S open_by_handle_at' or 'strace -e trace=open_by_handle_at' to observe if any processes invoke this syscall
    Affected if Processes are actively using open_by_handle_at, triggering the vulnerable code path in may_decode_fh()
  4. Check for mount namespace activity
    Observe for concurrent mount/umount operations while fhandle operations are in progress; use 'mount' and 'cat /proc/mounts' to list current mounts
    Affected if Mount operations occur concurrently with fhandle operations, creating the race condition window

A user is affected if running a vulnerable kernel version where the fhandle subsystem is accessible and open_by_handle_at is used while mount namespace operations are performed concurrently.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to 6.12.95 / 6.18.36 / 7.0.13 or later
Fixed in 6.12.956.18.367.0.13
Interim mitigation

Apply the kernel patch adding rcu_read_lock() around mount::mnt_ns access and use WRITE_ONCE() for writers; ensure systems with CONFIG_PREEMPTION or CONFIG_RCU_STRICT_GRACE_PERIOD are prioritized for patching.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-53341 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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