VulnerabilityPublished 16 Sep 2026Updated 5 Oct 2026

CVE-2026-89917: Linux kernel · KVM: arm64: Handle VNCR TLB invalidation race with vcpu_put() VNCR unmapping

Affects Linux kernelSource GCVE Database

Not known to be exploited.

Data as of 26 Oct 2026, 13:47 UTC

Severity

Medium

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.

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 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected 6.17.0-5.5 – 7.0.0-38.38 23 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected 6.17.0-1003.3 – 7.0.0-1017.17 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected 7.0.0-1003.3 – 7.0.0-1016.16 9 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 13 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gke`pkg:deb/ubuntu/linux-gke?arch=source&distro=resolute`Other threats	Affected 7.0.0-1002.3 – 7.0.0-1008.9 6 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 has been implemented in the Linux kernel to address this race condition by making the reset of vncr_tlb::cpu atomic and synchronizing unmapping operations. Users should apply the updated kernel versions containing this fix. Patch status is not explicitly confirmed in the provided data; therefore, check the vendor or distribution advisory for the latest remediation guidance.

Description

A race condition vulnerability in the Linux kernel's KVM implementation for arm64 was resolved. The issue involves a time-of-check to time-of-use (TOCTOU) race between VNCR TLB invalidation and vcpu_put() unmapping, which can lead to a BUG_ON() condition and potentially lethal effects. The fix involves making the reset of vncr_tlb::cpu atomic and synchronizing the unmapping operations to prevent concurrent access issues.

Impact

The vulnerability can cause kernel instability or crashes due to the BUG_ON() triggered by the race condition in VNCR TLB invalidation and unmapping. This affects the reliability of the KVM virtualization on arm64 architectures. There is no indication of code execution or privilege escalation from the provided data.

Summary

This vulnerability in the Linux kernel affects the KVM arm64 virtualization component. It arises from a race condition between VNCR TLB invalidation, which occurs under the MMU lock, and the vcpu_put() function, which unmaps the VNCR page without holding the MMU lock. The race leads to inconsistent states where vncr_tlb::cpu is checked and reset non-atomically, causing a TOCTOU pattern and a BUG_ON() in vcpu_put(). The fix moves the reset of vncr_tlb::cpu to a common atomic function and ensures unmapping is done unconditionally in vcpu_put(), preventing concurrent threads from causing inconsistent VNCR states.

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 24 Oct 2026, 20:14 UTC

Technical details

References

Community reviews

Related threats