CVE-2026-97971
Received Received - Intake

Reference Leak in Linux Kernel Namespace Handling

Publication date: 2026-09-25

Last updated on: 2026-09-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: nstree: check listing permission before taking a namespace reference legitimize_ns() takes a reference on the candidate namespace before may_list_ns() has decided whether the caller may see it. The __free(ns_put) cleanup on the denied path can drop the last reference to a mount namespace while we still hold the rcu read lock, and put_mnt_ns() may sleep there. This is the same problem commit 2ec2aff3c8e2 ("ns: make sure reference are dropped outside of rcu lock") fixed for the put_user() path. Neither ns_requested() nor may_list_ns() needs a reference, both only look at the namespace type and at the caller's own namespaces, so do the checks first and take the reference last. Splat: Voluntary context switch within RCU read-side critical section! WARNING: kernel/rcu/tree_plugin.h:332 at rcu_note_context_switch+0x238/0x2a0, CPU#5: a/3442 CPU: 5 UID: 1000 PID: 3442 Comm: a Not tainted 7.0.0-30-generic #30-Ubuntu PREEMPT(lazy) RIP: 0010:rcu_note_context_switch+0x238/0x2a0 Call Trace: <TASK> __schedule+0xcf/0x650 schedule+0x27/0x90 schedule_preempt_disabled+0x15/0x30 __mutex_lock.constprop.0+0x550/0xaf0 __mutex_lock_slowpath+0x13/0x20 mutex_lock+0x3b/0x50 exp_funnel_lock+0xb2/0x260 synchronize_rcu_expedited+0xe7/0x220 namespace_unlock+0x26a/0x320 put_mnt_ns+0xd3/0x120 mntns_put+0xe/0x20 do_listns+0x13e/0x560 __do_sys_listns+0x126/0x2d0 __x64_sys_listns+0x20/0x30 x64_sys_call+0x2366/0x2390 do_syscall_64+0x105/0x5a0 entry_SYSCALL_64_after_hwframe+0x76/0x7e </TASK>

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Meta Information

Published
2026-09-25
Last Modified
2026-09-25
Generated
2026-09-25
AI Q&A
2026-09-25
EPSS Evaluated
N/A
NVD
CVE-2026-97971
EUVD
EUVD-2026-86825

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 7.0.0

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a race condition in the namespace handling code. The function legitimize_ns() takes a reference on a namespace before checking if the caller has permission to list it. If permission is denied, the cleanup process may drop the last reference to the namespace while holding an RCU read lock, causing a sleep-in-atomic-context bug. This can lead to system instability or crashes.

Detection Guidance

This vulnerability is specific to the Linux kernel and relates to namespace handling. Detection requires checking kernel logs for RCU-related warnings or crashes during namespace operations. Monitor for splats like the one shown in the description, particularly around RCU context switches or mutex lock issues in namespace operations.

Impact Analysis

This vulnerability could allow a local attacker to cause a kernel crash or trigger a denial-of-service condition by exploiting the race condition. It may also lead to unexpected system behavior or instability, particularly in systems running unpatched Linux kernels.

Mitigation Strategies

Apply the latest kernel updates from your Linux distribution to ensure the patched version is installed. If immediate patching is not possible, restrict access to namespace operations via system policies or seccomp filters until the update is applied.

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