CVE-2026-99258: Linux kernel · x86/hyperv: Avoid using per-cpu output page in hv_apicid_to_vp_index()
Source GCVE Database
Not known to be exploited · fixed in bdba5f1b8bd0d18b1df61f769b559ed272902489 : update Linux kernel when convenient.
Data as of 3 Nov 2026, 13:28 UTC
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
Disclosed: evidence found.
CVE published 3 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 3 Nov 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in– |
AI-suggested
A fix has been implemented in the Linux kernel to use the input page for both input and output in the hv_apicid_to_vp_index() function, eliminating the use of unallocated output pages. Users should update to the fixed kernel version once available. No additional mitigation steps are indicated.
Description
A vulnerability in the Linux kernel's x86 Hyper-V code was fixed by changing the use of per-CPU output pages in the hv_apicid_to_vp_index() function. The function previously used separate per-CPU input and output pages, but in some configurations (SEV-SNP CoCo VMs without a paravisor), the output page was not allocated, causing the hypervisor to write output to unallocated guest memory. The fix involves using the input page for both input and output to avoid unallocated memory access.
References
- nvd.nist.gov/vuln/detail/CVE-2026-99258 (opens in a new tab)
- git.kernel.org/stable/c/2b561786c9076a892ef8b8f416c9828bc87ed44f (opens in a new tab)
- git.kernel.org/stable/c/7b74c117e2aac78e0f723e1c9c3644451c56b0d9 (opens in a new tab)
- git.kernel.org/stable/c/bc8ca0f4769627ae7d04e7ffdbd20de4f27a9bf9 (opens in a new tab)
- git.kernel.org/stable/c/bdba5f1b8bd0d18b1df61f769b559ed272902489 (opens in a new tab)