KVM: nVMX: Force MSR bitmap refresh if runtime eVMCS controls are modified
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Published
13 h ago
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Vulnerability description
CVE AI research
DayBreach AI Explanation
Verified against sourcesSources read
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Source agreement
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Evidence confidence
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Short explanation
A vulnerability exists in the Linux kernel KVM nVMX subsystem where the vmcs02 MSR bitmap is not forcibly refreshed when runtime eVMCS controls are modified. This can leave TPR in passthrough mode even when TPR virtualization is disabled.
Failure to refresh the bitmap allows L2 or L1 by proxy to read and write L0's TPR, compromising the integrity of the virtualization layer.
What should be done?
- Follow relevant vendor advisories and updates
- Review MSR bitmap refresh logic in the kernel code
- Keep runtime eVMCS controls updated
The sources give limited detail on some technical conditions. Review the chain of evidence below before deciding how to act.
Chain of evidence and sources
Linux çekirdeğindeki KVM nVMX alt sisteminde çalışma zamanı eVMCS kontrolleri değiştirildiğinde MSR bitmap yenilemesi zorlanmamaktadır.
Bitmap yenileme hatası, L2 veya L1'in L0 TPR değerlerini okumasına ve yazmasına olanak tanır.
Show the technical text from the sources
In the Linux kernel, the following vulnerability has been resolved: KVM: nVMX: Force MSR bitmap refresh if runtime eVMCS controls are modified Force a refresh of the vmcs02 MSR bitmap during nested VM-Enter if the runtime eVMCS controls (pin, primary, secondary, etc.) are being updated. If L1 isn't intercepting TPR writes, runs L2 with TPR virtualization, and then runs the same L2 with TPR virtualization disabled, KVM will fail to refresh msr_bitmap02 and leave TPR in passthrough mode even though TPR virtualization is disabled. I.e. failure to refresh the bitmap lets L2 (or L1 by proxy) read and write L0's TPR.
Explanation produced with the local gemini-flash-lite-latest model. Numerical metrics and the KEV, patch and exploit statuses are not determined by AI.
IMPACT: Affected Products and Software
RED HAT CSAF/VEX: Product Impact Check
SCORING: CVSS from Multiple Sources
CVSS Scores
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| SCORE | VERSION | SEVERITY | VECTOR | SOURCE |
|---|---|---|---|---|
| The sources have not yet published a verified CVSS metric. | ||||
Patch and Remediation Guide
Solution & Remediation Advisory
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Public exploit and active exploitation status
Verified exploit intelligence
No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.
Weakness Classification and Attack Patterns (CWE & CAPEC)
CWE - Common Weakness Enumeration
While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-98720 is associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-98720 weaknesses.
Official Sources and Advisories
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