VulnerabilityPublished 18 Oct 2026

CVE-2026-98720: Linux kernel · KVM: nVMX: Force MSR bitmap refresh if runtime eVMCS controls are modified

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in f6189e26d0237e47e2f04f9cb1e43fd19a9b2f3a : patch Linux kernel soon.

Data as of 26 Oct 2026, 10:12 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in f6189e26d0237e47e2f04f9cb1e43fd19a9b2f3a, 2db11598b59f16ddb6420693f9a4ac4efc3d4789, 2abb25273c82061dd4670690c81c319c03740bf6 +1

Exploitation evidence

Disclosed: evidence found.
CVE published 18 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.

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

Upgrade Linux kernel to f6189e26d0237e47e2f04f9cb1e43fd19a9b2f3a, 2db11598b59f16ddb6420693f9a4ac4efc3d4789, 2abb25273c82061dd4670690c81c319c03740bf6 or 1e497e3bdab6983deb68a1d26b488027deb4527f.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e, < f6189e26d0237e47e2f04f9cb1e43fd19a9b2f3a	Fixed in f6189e26d0237e47e2f04f9cb1e43fd19a9b2f3a
LinuxLinux	Affected ≥ 502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e, < 2db11598b59f16ddb6420693f9a4ac4efc3d4789	Fixed in 2db11598b59f16ddb6420693f9a4ac4efc3d4789
LinuxLinux	Affected ≥ 502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e, < 2abb25273c82061dd4670690c81c319c03740bf6	Fixed in 2abb25273c82061dd4670690c81c319c03740bf6
LinuxLinux	Affected ≥ 502d2bf5f2fd7c05adc2d4f057910bd5d4c4c63e, < 1e497e3bdab6983deb68a1d26b488027deb4527f	Fixed in 1e497e3bdab6983deb68a1d26b488027deb4527f
LinuxLinux	Affected =5.17	Fixed in–
Debiandebian/linux`pkg:deb/debian/linux`Other threats	Affected =5.17	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

This vulnerability has been fixed in the Linux kernel. The fix forces a refresh of the vmcs02 MSR bitmap during nested VM-Enter when runtime eVMCS controls are modified. Users should update to a Linux kernel version that includes the fix identified by the commits f6189e26d0237e47e2f04f9cb1e43fd19a9b2f3a, 2db11598b59f16ddb6420693f9a4ac4efc3d4789, 2abb25273c82061dd4670690c81c319c03740bf6, or 1e497e3bdab6983deb68a1d26b488027deb4527f. No other mitigation is indicated.

Description

A vulnerability in the Linux kernel's KVM nested virtualization (nVMX) component could cause the MSR bitmap to not refresh properly when runtime eVMCS controls are modified. This flaw allows a nested guest (L2) or the intermediate guest (L1) to read and write the host's (L0) Task Priority Register (TPR) when TPR virtualization is disabled, due to failure to update the MSR bitmap during nested VM-Enter transitions.

Impact

The vulnerability allows a nested guest or intermediate hypervisor to read and write the host's TPR register when it should be virtualized or inaccessible. This could lead to unintended privilege escalations or interference with host scheduling and interrupt handling, compromising the isolation between nested virtual machines and the host.

Summary

CVE-2026-98720 addresses a flaw in the Linux kernel's KVM nested virtualization implementation where the MSR bitmap (msr_bitmap02) is not refreshed during nested VM-Enter if runtime eVMCS controls such as pin, primary, or secondary controls are updated. Specifically, if the L1 hypervisor does not intercept TPR writes and runs L2 with TPR virtualization enabled and then disabled, the bitmap remains stale, leaving TPR in passthrough mode. This enables L2 or L1 to access L0's TPR registers directly, violating isolation guarantees.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 09:59 UTC

Technical details

References

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