CVE-2026-53345 KVM: Don't WARN if memory is dirtied without a vCPU when the VM is dying
A logic error in KVM triggers a kernel warning when SEV-ES VMs are destroyed, potentially causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53345?
CVE-2026-53345 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
KVM: Don't WARN if memory is dirtied without a vCPU when the VM is dying
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.
Weakness: CWE-401
Which versions are affected by CVE-2026-53345?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53345?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-53345 being exploited?
There is no known exploitation of CVE-2026-53345 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-91616, BELL-CVE-2026-53345, DEBIAN-CVE-2026-53345, GHSA-m28w-5q4v-5m48, ROOT-OS-DEBIAN-11-CVE-2026-53345, ROOT-OS-DEBIAN-12-CVE-2026-53345 and 3 more.