CVE-2026-99258
x86/hyperv: Avoid using per-cpu output page in hv_apicid_to_vp_index()
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.
INFO
Published Date :
Nov. 3, 2026, 12:17 p.m.
Last Modified :
Nov. 3, 2026, 12:17 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Affected Products
The following products are affected by CVE-2026-99258
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Update the Linux kernel to the latest version.
- Apply the specific patch for the hv_apicid_to_vp_index() function.
- Ensure per-cpu output pages are correctly allocated.
- Test the system for stability and security.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-99258.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes 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.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-99258 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-99258 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Nov. 03, 2026
Action Type Old Value New Value Added 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. Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/99xxx/CVE-2026-99258.json">CVE-2026-99258</a> Added Reference https://git.kernel.org/stable/c/2b561786c9076a892ef8b8f416c9828bc87ed44f Added Reference https://git.kernel.org/stable/c/7b74c117e2aac78e0f723e1c9c3644451c56b0d9 Added Reference https://git.kernel.org/stable/c/bc8ca0f4769627ae7d04e7ffdbd20de4f27a9bf9 Added Reference https://git.kernel.org/stable/c/bdba5f1b8bd0d18b1df61f769b559ed272902489