CVE-2026-46076
HighCVSS 7.9Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
A vulnerability in the Linux kernel has been resolved in KVM, which involved improper handling of VMMCALL calls when L1 did not want to intercept them. In such cases, KVM generates a #UD exception, allowing L2 to make hypercalls without L1's interaction.
Risk Assessment
The lack of proper interception of VMMCALL calls may lead to unauthorized access to hypervisor functions, posing a security risk to virtual environments.
Recommendation
It is recommended to update the Linux kernel to the latest version to patch this vulnerability and ensure proper interception of VMMCALL calls.
Original NVD description (English source)
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]