x86/hyperv: Avoid using per-cpu output page in hv_apicid_to_vp_index()
CVSS score
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EPSS probability
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Risk score
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Published
2 h ago
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Vulnerability description
DayBreach AI Explanation
Verified against sourcesSources read
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Source agreement
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Evidence confidence
%55
Short explanation
A vulnerability in the Linux kernel x86/hyperv subsystem has been addressed, involving hv_apicid_to_vp_index() using unallocated memory pages for hypervisor output.
This vulnerability leads to improper memory usage during hypervisor interactions in SEV-SNP CoCo virtual machines.
What should be done?
- Monitor for upstream kernel updates
- Follow vendor advisories for patching
Chain of evidence and sources
hv_apicid_to_vp_index() fonksiyonu per-cpu hypercall girdi ve çıktı sayfalarını kullanmaktadır.
Paravisor içermeyen SEV-SNP CoCo sanal makinelerinde çıktı sayfası tahsis edilmemektedir.
Show the technical text from the sources
In the Linux kernel, the following vulnerability has been resolved: x86/hyperv: Avoid using per-cpu output page in hv_apicid_to_vp_index() hv_apicid_to_vp_index() currently uses the per-cpu hypercall input and output pages. This function is called when running in VTL2 and when running in an SEV-SNP CoCo VM with no paravisor. In the former case, the output page is allocated, but in the latter case it is not, so the hypervisor stores the output VP index in memory that has not been allocated by the guest. Fix this by using the input page for both input and output. The hypercall has very small input and output, so sharing the same page for both is straightforward. An alternative fix is to allocate the per-cpu output page when running in an SEV-SNP CoCo guest, but this uses significantly more memory, particularly with larger vCPUs counts.
This explanation was compiled automatically from the source records. Scores, active exploitation, patch and exploit status come straight from the sources.
IMPACT: Affected Products and Software
RED HAT CSAF/VEX: Product Impact Check
SCORING: CVSS from Multiple Sources
CVSS Scores
The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.
| 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-2026-99258 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-2026-99258 weaknesses.
Official Sources and Advisories
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