medium 5.5

CVE-2026-53345 json

KVM: Don't WARN if memory is dirtied without a vCPU when the VM is dying

published 2026-07-01 4 mo ago modified 2026-11-06 2 d ago also EUVD-2026-40979

cvss: 5.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits: 0; none known

In the Linux kernel, the following vulnerability has been resolved:

When marking a page dirty, complain about not having a running/loaded vCPU if and only if the VM is still alive, i.e. its refcount is non-zero. This will allow fixing a memory leak for x86 SEV-ES guests without hitting what is effectively a false positive on the WARN.

For some SEV-ES VM-Exits, KVM keeps a writable mapping of a guest page across an exit to userspace, and typically unmaps the page on the next KVM_RUN. But if userspace never calls KVM_RUN after such an exit, then KVM needs to unmap the page when the vCPU is destroyed, which in turn triggers the WARN about not having a running vCPU.

Alternatively, SEV-ES could temporarily load the vCPU to suppress the WARN, as is done in nested_vmx_free_vcpu() (but for completely unrelated reasons; suppressing WARN from nested_put_vmcs12_pages() is pure happenstance). But loading a vCPU during destruction is gross (ideally nVMX code would be cleaned up), risks complicating the SEV-ES code (KVM would need to ensure the temporarily load()+put() only runs when the vCPU isn't already loaded), and is ultimately pointless.

The motivation for the WARN is to guard against KVM dirtying guest memory without pushing the corresponding GFN to the active vCPU's dirty ring, e.g. to ensure userspace doesn't miss a dirty page. But for the VM's refcount to reach zero, there can't be _any_ userspace mappings to the dirty ring, as mapping the dirty ring requires doing mmap() on the vCPU FD. I.e. if userspace had a valid mapping for the dirty ring, then the vCPU file and thus the owning VM would still be alive. And so since userspace can't possibly reach the dirty ring, whether or not KVM technically "misses" a push to the dirty ring is irrelevant.

Patch / fix

fixed in 1 distros 5 links 6

Linux Linux 6.1.191, 6.6.143, 6.12.94, 6.18.36, 7.0.13, 7.1

debian ubuntu suse opensuse azure linux

linux Debian 13 6.12.94-1
linux Debian 14 7.0.13-1

debian advisories DEBIAN-CVE-2026-53345

linux Ubuntu 24.04 LTS 6.8.0-146.146
linux Ubuntu 26.04 LTS 7.0.0-31.31
linux-aws Ubuntu 24.04 LTS 6.8.0-1066.69
linux-aws Ubuntu 26.04 LTS 7.0.0-1012.12
linux-gcp Ubuntu 24.04 LTS 6.8.0-1070.78
linux-gcp Ubuntu 26.04 LTS 7.0.0-1011.11
linux-gke Ubuntu 24.04 LTS 6.8.0-1065.73
linux-gke Ubuntu 26.04 LTS 7.0.0-1006.7

ubuntu advisories UBUNTU-CVE-2026-53345

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

kernel-rt Real Time Module 15 SP7 6.4.0-150700.7.72.1
kernel-syms-rt Real Time Module 15 SP7 6.4.0-150700.7.72.1
kernel-source-rt Real Time Module 15 SP7 6.4.0-150700.7.72.1
kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.78.1
kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.78.1
kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.78.1
kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.78.1
kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.78.1

suse advisories SUSE-SU-2026:3810-1 SUSE-SU-2026:3790-1 SUSE-SU-2026:23244-1 SUSE-SU-2026:23241-1 SUSE-SU-2026:23194-1 SUSE-SU-2026:23193-1

kernel-rt openSUSE Leap 16.0 6.12.0-160000.37.1
dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.37.1
kernel-64kb openSUSE Leap 16.0 6.12.0-160000.37.1
kernel-syms openSUSE Leap 16.0 6.12.0-160000.37.1
kernel-azure openSUSE Leap 16.0 6.12.0-160000.37.1
kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.37.1
kernel-source openSUSE Leap 16.0 6.12.0-160000.37.1
kernel-default openSUSE Leap 16.0 6.12.0-160000.37.1

opensuse advisories openSUSE-SU-2026:21555-1

kernel Azure Linux 3.0 6.6.143.1-1

azure linux advisories AZL-91616

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-53345 updated 2026-11-07

kernel: KVM: Don't WARN if memory is dirtied without a vCPU when the VM is dying

Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 2 d ago (2026-11-06)

Exploit prediction

0.12% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.1	5.5	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

Linux Linux

Classification

Weakness

CWE-401 Missing Release of Memory after Effective Lifetime

Technology feeds

Linux kernel rss critical rss

References

Sources

CVE List CVE-2026-53345
NVD CVE-2026-53345

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary