CVE-2026-89956: Linux kernel · s390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 26 Oct 2026, 17:16 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Exploitation evidence
Disclosed: evidence found.
CVE published 16 Sep 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 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther 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 corrects the locking mechanism by using the proper guests_lock mutex to guard access to the mdev_list. Users should update to a patched Linux kernel version that includes this fix. No additional mitigation steps are indicated by the vendor advisory.
Description
A concurrency control vulnerability in the Linux kernel's s390 vfio-ap driver was fixed by ensuring proper locking when accessing the list of ap_matrix_mdev objects. The issue involved missing the required guests_lock mutex when traversing or modifying the mdev_list, which could lead to kernel memory corruption or use-after-free conditions. The fix enforces correct locking order and removes redundant code related to trigger initialization.
References
- ubuntu.com/security/CVE-2026-89956 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-89956 (opens in a new tab)
- git.kernel.org/linus/7fa61c29850d05e40ca9ed41bfdf57673023f581 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-89956 (opens in a new tab)
- git.kernel.org/stable/c/0fd74477d05743d4cd9b25a3b667daa278d53b93 (opens in a new tab)
- git.kernel.org/stable/c/530ee1cc71562b6799b9ece187b6c1b757a2c6fa (opens in a new tab)
- git.kernel.org/stable/c/647916988272fe5ecb4bb30cd02b51af9960618a (opens in a new tab)
- git.kernel.org/stable/c/7fa61c29850d05e40ca9ed41bfdf57673023f581 (opens in a new tab)