CVE-2026-99065: Linux kernel · cgroup/cpuset: Handle cpu hotplug race in guarantee_active_cpus()
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 28 Oct 2026, 01:42 UTC
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.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.10linuxpkg:deb/ubuntu/linux?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=stonkingOther threats | Affected
| 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 is available that adds a NULL check in guarantee_active_cpus() to prevent the NULL pointer dereference. Users should apply the updated Linux kernel versions that include this fix. No additional mitigation steps are indicated.
Description
CVE-2026-99065 is a race condition vulnerability in the Linux kernel's cgroup cpuset subsystem related to CPU hotplug handling. The issue arises because the cpuset hotplug operation became synchronous, removing previous race handling code, but a subsequent change caused a race to reappear between cpu_active_mask updates and cpuset effective_cpus updates. This race can lead to the top cpuset having no active CPU, resulting in a NULL pointer dereference. The vulnerability affects specific Linux kernel versions and has been fixed by reintroducing a NULL check in guarantee_active_cpus().
References
- ubuntu.com/security/CVE-2026-99065 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-99065 (opens in a new tab)
- git.kernel.org/stable/c/23b1ab15ca91f2cffaf149d9bb0fafeb700c7db2 (opens in a new tab)
- git.kernel.org/stable/c/8d88d3221204fbb1b6dc2c0f2f2181fe49126639 (opens in a new tab)
- git.kernel.org/stable/c/a21c255159bfe0034740292e10d2e258feeeb10d (opens in a new tab)