CVE-2026-89775: Linux kernel · KVM: arm64: Handle negative S1 walk levels in VNCR TLB size evaluation
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.3 Critical.
Data as of 26 Oct 2026, 13:47 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 14% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:HExploitation 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 for this vulnerability has been implemented in the Linux kernel. Users should apply the official kernel updates that include the patch for CVE-2026-89775. The affected versions listed should be upgraded to patched versions as soon as possible to mitigate the risk. No additional mitigation steps are indicated beyond applying the official fix.
Description
A vulnerability in the Linux kernel's KVM arm64 code related to handling negative S1 walk levels in VNCR TLB size evaluation has been resolved. The issue arises because the function pgshift_level_to_ttl() does not correctly handle negative levels, leading to an invalid TLB invalidation size of zero when the MMU is off. This flaw affects specific Linux kernel versions and has been assigned CVE-2026-89775 with a high CVSS score of 9.3.
References
- ubuntu.com/security/CVE-2026-89775 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-89775 (opens in a new tab)
- git.kernel.org/linus/8053393680d4fa3eb962667d2be95dd39f0940e5 (opens in a new tab)
- openwall.com/lists/oss-security/2026/09/16/14 (opens in a new tab)
- git.kernel.org/stable/c/1c9fca34b9625a67a7f1a03c8604f3df760c6c49 (opens in a new tab)
- git.kernel.org/stable/c/8053393680d4fa3eb962667d2be95dd39f0940e5 (opens in a new tab)
- git.kernel.org/stable/c/be54a70067c7dbe1381157e8a238fa4b16ea9c05 (opens in a new tab)