CVE-2026-99040
Received
Received - Intake
Race Condition in Linux Kernel KEYS Subsystem
Vulnerability report for CVE-2026-99040, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-23
Last updated on: 2026-10-23
Assigner: kernel.org
Description
Description
In the Linux kernel, the following vulnerability has been resolved:
KEYS: Fix add_key() race with keyring restriction
__key_create_or_update() snapshots keyring->restrict_link before taking
the destination keyring's semaphore. keyring_restrict() installs a
restriction while holding that semaphore.
This allows a writer to observe no restriction, wait for the keyring
owner to install a reject-all restriction and return successfully, and
then link a key using the stale NULL snapshot. The writer only needs
write permission on the destination keyring.
Move the restrict_link read after __key_link_lock() and
__key_link_begin(). The read and the subsequent restriction check are
then serialized with restriction installation by keyring->sem.
The race was reproduced on v7.2.8 in 19 executions where restriction
installation returned before the link completed. All 19 linked the key
despite the reject-all restriction. With this change, 312 executions
reached the same ordering and every add_key() call failed with -EPERM.
The issue was found by manual concurrency analysis assisted by AI-based
analysis and independently verified with a QEMU reproducer and kernel
instrumentation.
CVSS Scores
EPSS Scores
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| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| Linux | Linux | 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c |
| Linux | Linux | 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c |
| Linux | Linux | 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c |
| Linux | Linux | 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c |
| Linux | Linux | 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c |
| Linux | Linux | 4.7 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
