VulnerabilityPublished 23 Oct 2026

CVE-2026-99040: Linux kernel · KEYS: Fix add_key() race with keyring restriction

Source GCVE Database

Authoritative record:CVE-2026-99040· High

Not known to be exploited · fixed in f99399b48e3edd6851fac34cd329bab9f1f33baf : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:05 UTC

Severity

High

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in f99399b48e3edd6851fac34cd329bab9f1f33baf, dd3ea3fcba7c75493760cdbccd35f029597e8d5e, da0b595d8e6e2dd798f6e34e09dc51a13b888514 +2

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-xfxp-jqfr-m4g5

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c, < f99399b48e3edd6851fac34cd329bab9f1f33baf	Fixed in f99399b48e3edd6851fac34cd329bab9f1f33baf
LinuxLinux	Affected ≥ 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c, < dd3ea3fcba7c75493760cdbccd35f029597e8d5e	Fixed in dd3ea3fcba7c75493760cdbccd35f029597e8d5e
LinuxLinux	Affected ≥ 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c, < da0b595d8e6e2dd798f6e34e09dc51a13b888514	Fixed in da0b595d8e6e2dd798f6e34e09dc51a13b888514
LinuxLinux	Affected ≥ 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c, < 11516a0c402a6c1fa52254aa70d8d65fb921e59e	Fixed in 11516a0c402a6c1fa52254aa70d8d65fb921e59e
LinuxLinux	Affected ≥ 5ac7eace2d00eab5ae0e9fdee63e38aee6001f7c, < 305f1828b871dd46bf41addeb6f11d2c162dcb25	Fixed in 305f1828b871dd46bf41addeb6f11d2c162dcb25
LinuxLinux	Affected =4.7	Fixed in–

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.

References

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