CVE-2026-98653 KVM: s390: Fix _gaccess_shadow_fault()
A flaw in Linux kernel KVM s390 allows a local attacker to cause a denial of service by triggering an error in nested guest memory shadowing.
- 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-2026-98653?
CVE-2026-98653 is a denial of service 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: s390: Fix _gaccess_shadow_fault()
In some circumstances, it is possible that the page of nested guest memory that is being shadowed is not present at all in the parent guest gmap. dat_entry_walk() will not find any leaf entry and return with -ENOENT, which will erroneously be propagated all the way to userspace.
Fix by manually calling gmap_link() on the memory of the nested guest that is being shadowed if the mapping was not already present.
Which versions are affected by CVE-2026-98653?
How do I fix CVE-2026-98653?
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-2026-98653 being exploited?
There is no known exploitation of CVE-2026-98653 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-98653, GHSA-v97x-654r-4f82, UBUNTU-CVE-2026-98653.