Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-05-27T00:00:00 kernel: KVM: nSVM: Raise #UD if unhandled VMMCALL isn't intercepted by L1 7.0 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H CWE-475

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]

A flaw was found in the Kernel-based Virtual Machine (KVM) nSVM module of the Linux kernel. This vulnerability occurs when an unhandled VMMCALL is not properly intercepted by the Level 1 (L1) hypervisor. A malicious Level 2 (L2) guest operating system could exploit this by making specific hypercalls, leading to an Undefined Opcode exception (#UD) in the host. This could potentially result in a denial of service for the host system.

Red Hat Enterprise Linux 10 Affected kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Not affected kernel Red Hat Enterprise Linux 8 Not affected kernel-rt Red Hat Enterprise Linux 9 Affected kernel Red Hat Enterprise Linux 9 Affected kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-46076 https://nvd.nist.gov/vuln/detail/CVE-2026-46076 https://lore.kernel.org/linux-cve-announce/2026052759-CVE-2026-46076-699a@gregkh/T