CVE-2026-98863 KVM: x86: Re-pend GET_NESTED_STATE_PAGES if getting said pages fails
A flaw in Linux KVM allows local attackers to exploit stale page mappings, potentially leading to code execution or privilege escalation.
- 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-2026-98863?
CVE-2026-98863 is an use after free vulnerability in Linux, published on 18 Oct 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: x86: Re-pend GET_NESTED_STATE_PAGES if getting said pages fails
Re-pend GET_NESTED_STATE_PAGES before exiting to userspace if getting the nested pages fails in the KVM_RUN path. If userspace re-runs the vCPU, and vmcs02 holds valid PFNs from the *previous* run of L2, then KVM could re-enter L2 with stale, unpinned PFNs mapped into e.g. the vAPIC page.
Note, both SVM and VMX (as of commit 11722439fb20 ("KVM: nVMX: Ensure KVM_REQ_GET_NESTED_STATE_PAGES is cleared on VM-Exit") ensure the request is cleared on VM-Exit (including the "forced" case), i.e. there is no risk of double-mapping due to emulated VMLAUNCH/VMRESUME/VMRUN *and* the request trying to map the nested pages.
Which versions are affected by CVE-2026-98863?
How do I fix CVE-2026-98863?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-98863 being exploited?
There is no known exploitation of CVE-2026-98863 in the wild and no public exploit code.
Sources
Also known as AZL-109449, BELL-CVE-2026-98863, DEBIAN-CVE-2026-98863, GHSA-8v5w-2f74-jcch, UBUNTU-CVE-2026-98863.