CVE-2026-99040 is a vulnerability in Linux Kernel
Published on October 23, 2026
KEYS: Fix add_key() race with keyring restriction
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.
Products Associated with CVE-2026-99040
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Affected Versions
Linux:- Version 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c and below 305f1828b871dd46bf41addeb6f11d2c162dcb25 is affected.
- Version 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c and below f99399b48e3edd6851fac34cd329bab9f1f33baf is affected.
- Version 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c and below 11516a0c402a6c1fa52254aa70d8d65fb921e59e is affected.
- Version 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c and below da0b595d8e6e2dd798f6e34e09dc51a13b888514 is affected.
- Version 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c and below dd3ea3fcba7c75493760cdbccd35f029597e8d5e is affected.
- Version 4.7 is affected.
- Before 4.7 is unaffected.
- Version 6.6.160, <= 6.6.* is unaffected.
- Version 6.12.113, <= 6.12.* is unaffected.
- Version 6.18.57, <= 6.18.* is unaffected.
- Version 7.2.11, <= 7.2.* is unaffected.
- Version 7.3, <= * is unaffected.