CVE-2026-46076 KVM: nSVM: Raise #UD if unhandled VMMCALL isn't intercepted by L1
A guest VM can bypass L1 hypervisor controls by executing VMMCALL instructions that are not properly intercepted, potentially violating isolation boundaries.
- 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-2026-46076?
CVE-2026-46076 is a high-severity vulnerability in Linux kernel, published on 27 May 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: nSVM: Raise #UD if unhandled VMMCALL isn't intercepted by L1
Explicitly synthesize a #UD for VMMCALL if L2 is active, L1 does NOT want to intercept VMMCALL, nested_svm_l2_tlb_flush_enabled() is true, and the hypercall is something other than one of the supported Hyper-V hypercalls. When all of the above conditions are met, KVM will intercept VMMCALL but never forward it to L1, i.e. will let L2 make hypercalls as if it were L1.
The TLFS says a whole lot of nothing about this scenario, so go with the architectural behavior, which says that VMMCALL #UDs if it's not intercepted.
Opportunistically do a 2-for-1 stub trade by stub-ifying the new API instead of the helpers it uses. The last remaining "single" stub will soon be dropped as well.
[sean: rewrite changelog and comment, tag for stable, remove defunct stubs]
Weakness: CWE-863
Which versions are affected by CVE-2026-46076?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-46076?
Apply the vendor's patch.
Is CVE-2026-46076 being exploited?
There is no known exploitation of CVE-2026-46076 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-88614, BELL-CVE-2026-46076, DEBIAN-CVE-2026-46076, GHSA-gj33-hwgc-v3v8, ROOT-OS-UBUNTU-2404-CVE-2026-46076, UBUNTU-CVE-2026-46076.