CVE-2026-89923: Linux kernel · KVM: s390: Free guest debug data on vcpu destroy
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 26 Oct 2026, 14:05 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 11% 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 unconditionally clears guest debug data on vCPU destruction. Users should update to patched versions of the Linux kernel where this issue is resolved. Since this is a kernel-level fix, applying the vendor-provided kernel updates is the recommended remediation.
Description
A vulnerability in the Linux kernel's KVM subsystem for s390 architecture causes memory leaks of guest debug data when a virtual CPU (vCPU) is destroyed while hardware breakpoints remain armed. This occurs because the function to clear debug data is only called when debugging is explicitly changed or disabled, not on vCPU destruction. The leak involves several buffers and can accumulate over the lifetime of the virtual machine, potentially leading to resource exhaustion. A fix has been implemented to clear debug data unconditionally on vCPU destruction.
References
- ubuntu.com/security/CVE-2026-89923 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-89923 (opens in a new tab)
- git.kernel.org/linus/e7f698b09d4a7c36b299acf680fc50fe868e2bcd (opens in a new tab)
- msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-89923.json (opens in a new tab)
- support.microsoft.com/lifecycle (opens in a new tab)
- first.org/cvss (opens in a new tab)