VulnerabilityPublished 26 Oct 2026Updated 27 Oct 2026

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

Affects Linux kernelSource GCVE Database

Authoritative record:CVE-2026-99040· High

Not known to be exploited.

Data as of 28 Oct 2026, 01:44 UTC

Severity

High

Rated by Threat Radar · CVSS not yet scored by NVD

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.

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.10linux`pkg:deb/ubuntu/linux?arch=source&distro=stonking`Other threats	Affected 7.0.0-14.14 – 7.3.0-9.9 6 affected builds	Fixed in–
Ubuntu 26.10linux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=stonking`Other threats	Affected 7.0.0-1004.4 – 7.3.0-1003.3 5 affected builds	Fixed in–
Ubuntu 26.10linux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=stonking`Other threats	Affected 7.0.0-1004.4 – 7.3.0-1003.3 5 affected builds	Fixed in–
Ubuntu 26.10linux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=stonking`Other threats	Affected =7.0.0-1004.4 =7.3.0-1002.3 =7.3.0-1003.4	Fixed in–
Ubuntu 26.10linux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=stonking`Other threats	Affected 7.0.0-1003.3 – 7.3.0-1003.3 5 affected builds	Fixed in–
Ubuntu 26.10linux-oracle`pkg:deb/ubuntu/linux-oracle?arch=source&distro=stonking`Other threats	Affected 7.0.0-1003.3 – 7.3.0-1003.3 5 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix for this race condition has been implemented by changing the order of operations in add_key() to ensure serialization of restriction checks with restriction installation. Users should apply the updated Linux kernel versions that include this fix. Since the vulnerability is resolved in patched versions, no additional mitigation is required beyond updating to a fixed kernel release.

Description

CVE-2026-99040 is a race condition vulnerability in the Linux kernel's key management subsystem. It involves a timing issue in the add_key() function where a writer can bypass keyring restrictions by exploiting a race between reading the restriction and linking a key. The flaw allows a writer with write permission on a destination keyring to link a key despite a reject-all restriction being installed. The issue was confirmed through concurrency testing and reproducer tools.

Impact

An attacker with write permission on a destination keyring can bypass keyring restrictions and link keys despite reject-all restrictions. This could lead to unauthorized key additions, potentially undermining security policies relying on keyring restrictions. The impact is limited to users with write access to the keyring, and no evidence of exploitation in the wild is reported.

Summary

This vulnerability in the Linux kernel's key management system arises from a race condition in add_key() where __key_create_or_update() snapshots the keyring's restrict_link field before acquiring the destination keyring's semaphore. Since keyring_restrict() installs restrictions while holding this semaphore, a writer can observe no restriction, wait for the owner to install a reject-all restriction, and then link a key using a stale NULL snapshot. This allows bypassing the restriction with only write permission on the keyring. The fix moves the restrict_link read after locking functions to serialize the read with restriction installation, preventing the race. The issue was reproduced on kernel version 7.2.8 and verified with QEMU and kernel instrumentation.

GCVE source: db.gcve.eu
OSV ID: UBUNTU-CVE-2026-99040
Osv Schema Version: 1.7.0
Ecosystems: Ubuntu:Pro:14.04:LTS, Ubuntu:Pro:16.04:LTS, Ubuntu:16.04:LTS, Ubuntu:Pro:18.04:LTS, Ubuntu:18.04:LTS, Ubuntu:Pro:FIPS-updates:18.04:LTS, Ubuntu:Pro:FIPS:18.04:LTS, Ubuntu:Pro:20.04:LTS, Ubuntu:20.04:LTS, Ubuntu:Pro:FIPS-updates:20.04:LTS, Ubuntu:Pro:FIPS:20.04:LTS, Ubuntu:22.04:LTS, Ubuntu:Nvidia-BlueField:22.04:LTS, Ubuntu:Pro:Realtime:22.04:LTS, Ubuntu:Pro:FIPS-preview:22.04:LTS, Ubuntu:Pro:FIPS-updates:22.04:LTS, Ubuntu:24.04:LTS, Ubuntu:Nvidia-BlueField:24.04:LTS, Ubuntu:Pro:Realtime:24.04:LTS, Ubuntu:Pro:FIPS-updates:24.04:LTS, Ubuntu:26.10, Ubuntu:26.04:LTS

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Oct 2026, 01:44 UTC

Technical details

References

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