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Vulnerabilities

Vulnerability · CVE-2026-99040

KEYS: Fix add_key() race with keyring restriction

Published Oct 23, 2026 · catalog updated Oct 30, 2026 · Linux Linux

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-99040. EPSS is 0.19%. Act only if a listed version of Linux Linux is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Low—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.19%
Remediation
Advisory link
Affected products
Ubuntu:16.04:LTS linux-hwe-edge · Ubuntu:18.04:LTS linux-aws-5.0 · Ubuntu:18.04:LTS linux-aws-5.3 · Ubuntu:Pro:14.04:LTS linux-azure · Ubuntu:Pro:16.04:LTS linux-aws-hwe · Ubuntu:Pro:16.04:LTS linux-azure

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Ubuntu:16.04:LTS linux-hwe-edge4.8.0-28.30~16.04.1, 4.8.0-30.32~16.04.1, 4.8.0-32.34~16.04.1
  • Ubuntu:18.04:LTS linux-aws-5.05.0.0-1021.24~18.04.1, 5.0.0-1022.25~18.04.1, 5.0.0-1023.26~18.04.1
  • Ubuntu:18.04:LTS linux-aws-5.35.3.0-1016.17~18.04.1, 5.3.0-1017.18~18.04.1, 5.3.0-1019.21~18.04.1
  • Ubuntu:Pro:14.04:LTS linux-azure4.15.0-1023.24~14.04.1, 4.15.0-1030.31~14.04.1, 4.15.0-1031.32~14.04.1
  • Ubuntu:Pro:16.04:LTS linux-aws-hwe4.15.0-1030.31~16.04.1, 4.15.0-1031.33~16.04.1, 4.15.0-1032.34~16.04.1
  • Ubuntu:Pro:16.04:LTS linux-azure4.11.0-1009.9, 4.11.0-1011.11, 4.11.0-1013.13
  • Ubuntu:Pro:16.04:LTS linux-gcp4.10.0-1004.4, 4.10.0-1006.6, 4.10.0-1007.7
  • Ubuntu:Pro:16.04:LTS linux-hwe4.8.0-36.36~16.04.1, 4.8.0-39.42~16.04.1, 4.8.0-41.44~16.04.1
  • Ubuntu:Pro:16.04:LTS linux-oracle4.15.0-1007.9~16.04.1, 4.15.0-1008.10~16.04.1, 4.15.0-1009.11~16.04.1
  • Ubuntu:Pro:18.04:LTS linux4.13.0-16.19, 4.13.0-17.20, 4.13.0-25.29
  • Ubuntu:Pro:18.04:LTS linux-aws4.15.0-1001.1, 4.15.0-1003.3, 4.15.0-1005.5
  • Ubuntu:Pro:18.04:LTS linux-aws-5.45.4.0-1018.18~18.04.1, 5.4.0-1020.20~18.04.2, 5.4.0-1022.22~18.04.1
  • vendor Linux Linuxversion unspecified

How to fix CVE-2026-99040

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-99040. EPSS is 0.19%. Act only if a listed version of Linux Linux is installed.

Which versions are affected?

Compare what you have installed with 4.8.0-28.30~16.04.1, 4.8.0-30.32~16.04.1, 4.8.0-32.34~16.04.1, 5.0.0-1021.24~18.04.1, 5.0.0-1022.25~18.04.1, 5.0.0-1023.26~18.04.1, 5.3.0-1016.17~18.04.1, 5.3.0-1017.18~18.04.1, 5.3.0-1019.21~18.04.1, 4.15.0-1023.24~14.04.1, 4.15.0-1030.31~14.04.1, 4.15.0-1031.32~14.04.1, 4.15.0-1030.31~16.04.1, 4.15.0-1031.33~16.04.1, 4.15.0-1032.34~16.04.1, 4.11.0-1009.9, 4.11.0-1011.11, 4.11.0-1013.13. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.19%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Ubuntu security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 23, 2026 · Tenable CVE Database

    Detected

    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 re

  2. Oct 23, 2026 · CVE.org

    Updated

    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 re

  3. Oct 30, 2026 · OpenSSF OSV / OSV Scanner

    Updated

    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 re

Sources

  • CVE.orgVulnerability recordCVE-2026-99040

    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 holdi

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-99040

    30-day exploitation probability 0.19%

    first.org
  • OpenSSF OSV / OSV ScannerPackage advisoryUBUNTU-CVE-2026-99040
    osv.dev
  • Tenable CVE DatabaseVulnerability recordCVE-2026-99040

    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 re

    tenable.com

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSOct 31, 2026
  • OpenSSF OSV / OSV ScannerOct 30, 2026
  • CVE.orgOct 25, 2026
  • Tenable CVE DatabaseOct 23, 2026