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VulnerabilityPublished Updated

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

Affects Linux kernelSource GCVE Database

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Authoritative record:CVE-2026-99258· Medium

Not known to be exploited.

Data as of 5 Nov 2026, 00:01 UTC

Severity
Medium

Rated by Threat Radar · CVSS not yet scored by NVD

Thin evidence

One scorer or none
EPSS
0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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 4 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
Ubuntu 26.10linuxpkg:deb/ubuntu/linux?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-14.14 – 7.3.0-10.10
7 affected builds
Fixed in–
Ubuntu 26.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1004.4 – 7.3.0-1004.4
6 affected builds
Fixed in–
Ubuntu 26.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1004.4 – 7.3.0-1004.4
6 affected builds
Fixed in–
Ubuntu 26.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1004.4 – 7.3.0-1004.5
4 affected builds
Fixed in–
Ubuntu 26.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1003.3 – 7.3.0-1004.4
6 affected builds
Fixed in–
Ubuntu 26.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1003.3 – 7.3.0-1004.4
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 is available that changes the hv_apicid_to_vp_index() function to use the input page for both input and output, preventing writes to unallocated memory. Users should apply the updated Linux kernel versions that include this fix. No alternative mitigation is required as the patch addresses the root cause directly.

Description

A vulnerability in the Linux kernel's x86 Hyper-V code involves improper use of per-CPU output pages in the hv_apicid_to_vp_index() function. This function uses per-CPU hypercall input and output pages, but in certain virtual machine configurations, the output page is not allocated, leading to the hypervisor writing output to unallocated memory. The issue is fixed by using the input page for both input and output, avoiding unallocated memory usage.

References

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