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VulnerabilityPublished

CVE-2026-99258: Linux kernel · x86/hyperv: Avoid using per-cpu output page in hv_apicid_to_vp_index()

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in bdba5f1b8bd0d18b1df61f769b559ed272902489 : update Linux kernel when convenient.

Data as of 3 Nov 2026, 11:58 UTC

Severity
Medium

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

Thin evidence

One scorer or none
Patch
Available – fixed in bdba5f1b8bd0d18b1df61f769b559ed272902489, bc8ca0f4769627ae7d04e7ffdbd20de4f27a9bf9, 7b74c117e2aac78e0f723e1c9c3644451c56b0d9 +3

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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 3 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • >=6.12.41 <6.12.115
  • >=6.15.3 <6.16
Fixed in
  • bdba5f1b8bd0d18b1df61f769b559ed272902489
  • bc8ca0f4769627ae7d04e7ffdbd20de4f27a9bf9
  • 7b74c117e2aac78e0f723e1c9c3644451c56b0d9
  • 6.16
  • 6.12.115
  • 2b561786c9076a892ef8b8f416c9828bc87ed44f
LinuxLinuxAffected
  • =6.16
Fixed in–

AI-suggested

The vulnerability has been fixed in Linux kernel versions 6.12.115, 6.16, and 6.15.3 and later. Users should upgrade to these fixed versions or later to mitigate the issue. No additional mitigation actions are required beyond applying the official kernel updates.

Description

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.

References

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