CVE-2026-74516
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- CVE-2026-74516
CVE Details
| Release Date: | 2026-08-15 | |
| Impact: | Moderate | What is this? |
Description
In the Linux kernel, the following vulnerability has been resolved:
KVM: SVM: Update x2APIC MSR intercepts if AVIC is inhibited while L2 is active
Always update x2APIC MSR intercepts for L1 when AVIC is deactivated, even
if L2 is active and KVM is using a separate MSR bitmap to run L2. If AVIC
is fully enabled prior to running L2, and is then inhibited while L2 is
active (for a VM-scoped inhibit), then KVM will run L1 with AVIC disabled,
but with x2APIC MSR intercepts disabled, i.e. will allow L1 to read most of
the host's APIC state, send arbitrary interrupts, change task priority, and
ultimately trivially DoS the host.
E.g. sending a self-IPI in L1 on HYPERV_REENLIGHTENMENT_VECTOR, 0xee, with
CONFIG_HYPERV=n in the host kernel as a "safe" PoC, yields:
Spurious interrupt (vector 0xee) on CPU#425. Acked
And hacking KVM to abuse kvm_set_posted_intr_wakeup_handler() to register a
handler and WARN on POSTED_INTR_WAKEUP_VECTOR yields:
------------[ cut here ]------------
WARNING: arch/x86/kvm/svm/svm.c:5594 at pi_wakeup_handler+0x9/0x10 [kvm_amd], CPU#156: nested_x2apic_t/316940
CPU: 156 UID: 0 PID: 316940 Comm: nested_x2apic_t Tainted: G S U
Tainted: [S]=CPU_OUT_OF_SPEC, [U]=USER
Hardware name: Google Astoria-Turin/astoria, BIOS 0.20260209.0-0 02/09/2026
RIP: 0010:pi_wakeup_handler+0x9/0x10 [kvm_amd]
Call Trace:
See more information about CVE-2026-74516 from MITRE CVE dictionary and NIST NVD
NOTE: The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 metrics
| Base Score: | 7.0 |
| Vector String: | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H |
| Version: | 3.1 |
| Attack Vector: | Local |
| Attack Complexity: | High |
| Privileges Required: | Low |
| User Interaction: | None |
| Scope: | Unchanged |
| Confidentiality Impact: | High |
| Integrity Impact: | High |
| Availability Impact: | High |
Errata information
| Platform | Errata | Release Date |
| Oracle Linux version 10 (kernel-uek) | ELSA-2026-500248 | 2026-09-04 |
| Oracle Linux version 9 (kernel-uek) | ELSA-2026-500248 | 2026-09-04 |
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