Unknown

CVE-2026-99082 — KVM: x86: Use active memslots for the per-vCPU MMIO cache

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Use active memslots for the per-vCPU MMIO cache KVM tags the per-vCPU MMIO cache with a memslot generation so that a memslot update invalidates cached MMIO information. Both the fill and validation paths use kvm_memslots(), which unconditionally selects address space 0, even when the vCPU is running in SMM and using address space 1. Commit 56f17dd3fbc4 ("kvm: x86: fix stale mmio cache bug") added the memslot generation to the cache key so that a memslot update could not leave a stale entry valid. When commit 699023e23965 ("KVM: x86: add SMM to the MMU role, support SMRAM address space") added the SMM address space, these helpers were not converted to use the active memslots. Consequently, an update to the SMM memslots can leave an entry from the old SMM address space apparently valid after the vCPU returns to the normal address space. A guest can then cause an access to valid RAM at the same GFN to be returned to userspace as KVM_EXIT_MMIO. Completing that exit through the VMM's RAM address space writes the backing page without going through KVM's write-tracking path. If the page backs a nested EPT table, KVM can continue using shadow translations derived from the old contents. The WARN_ON_ONCE() in kvm_mmu_write_protect_fault() catches this invalid cache and memslot combination. Use the vCPU's active memslots when caching and validating the entry. Memslot generations are unique across address spaces, so the generation also distinguishes the normal and SMM views. This matches the MMIO SPTE cache, which already uses kvm_vcpu_memslots(). On an unpatched current-mainline kernel, a regression test that fills the cache in SMM and updates only the SMM memslots fails the intended RAM write and triggers the kvm_mmu_write_protect_fault() warning. With this change, the same test completes the RAM write without a warning. The x86/smm_test, set_memory_region_test, and memslot_modification_stress_test selftests also pass.

Published Oct 23, 2026 · Updated Oct 23, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

No scoring signals.

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 699023e239658e62da6f42f47d31b54788521ec1 and < a63f79d9da9468952396af73e1e53330845cf876≥ 699023e239658e62da6f42f47d31b54788521ec1 and < 7fd4e64f4bbc8c35ae8f0d2a1fb5b77a76d5b4fd≥ 699023e239658e62da6f42f47d31b54788521ec1 and < 2566780c684c9c21241d409d790087c73070f312≥ 699023e239658e62da6f42f47d31b54788521ec1 and < e792a9ace39d2812a5b342a1987186c7bc653204≥ 699023e239658e62da6f42f47d31b54788521ec1 and < b3e6212dea2e4328a841ceb37f377583176dc735version 4.2	Vulnerable	CVE Program (cve.org) e CISA ADP

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 23, 2026
Affected products added · linux/linux
Oct 23, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Received
Oct 23, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 23, 2026 · Alertas do Telegram
CVE published
Oct 23, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 23, 2026 – Oct 23, 2026
1× Official description updated · Oct 23, 2026 – Oct 23, 2026

References

5 on the record

git.kernel.org/stable/c/b3e6212dea2e4328a841ceb37f377583176dc735
NIST National Vulnerability Database
git.kernel.org/stable/c/e792a9ace39d2812a5b342a1987186c7bc653204
NIST National Vulnerability Database
git.kernel.org/stable/c/2566780c684c9c21241d409d790087c73070f312
NIST National Vulnerability Database
git.kernel.org/stable/c/7fd4e64f4bbc8c35ae8f0d2a1fb5b77a76d5b4fd
NIST National Vulnerability Database
git.kernel.org/stable/c/a63f79d9da9468952396af73e1e53330845cf876
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Unknown CVE-2026-99086 dm-integrity: validate the superblock on resume 7h
Unknown CVE-2026-99087 dm-integrity: fix NULL pointer dereference when the 'R' flag is used 7h
Unknown CVE-2026-99079 net/mlx5e: Prevent stale XSK buffer release on refill retry 7h
Unknown CVE-2026-99080 fs: Free any excess xarray nodes in clear_inode() 7h
Unknown CVE-2026-99081 bnxt_en: fix DMA mapping length for padded small packets 7h
Unknown CVE-2026-99083 ksmbd: fix heap out-of-bounds write in krb5_authenticate() 7h

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No FIRST EPSS score.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-99082 is "KVM: x86: Use active memslots for the per-vCPU MMIO cache", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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