# CVE-2026-81627: QEMU VAPIC setup hypercall memory validation bypass

Source: https://junglewise.ai/threats/cve-2026-81627-qemu-vapic-setup-hypercall-memory-validation-bypass  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-18. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-81627 · Severity: high · CVSS 8.2 · Published 2026-09-18

QEMU, an open-source machine emulator used to run virtual machines, contains a flaw in its VAPIC (Virtual APIC) feature that allows a privileged guest user to bypass SMRAM (System Management RAM) security protections on Q35/KVM machines. An attacker with root access in a guest operating system can exploit this to inject malicious code into System Management Mode memory, potentially gaining complete control over the host system's security functions.

Technologies: [Qemu](https://junglewise.ai/threats/technologies/qemu). Vendors: [Qemu](https://junglewise.ai/threats/vendors/qemu).

## Quick answers

**Is CVE-2026-81627 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-81627 being exploited in the wild.

**How severe is CVE-2026-81627?** High severity, with a CVSS score of 8.2, published 18 September 2026.

**Which products and versions are affected?** Qemu <UNKNOWN>.

**Is there a fix for CVE-2026-81627?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-81627 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-81627?** Check whether you run Qemu at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in hw/i386/vapic.c, where the VAPIC setup hypercall fails to validate that a writable RAM alias remains within the option ROM window boundary. An attacker with guest root privileges on a Q35/KVM machine can invoke this hypercall to position the alias outside the expected range, causing it to overlap locked SMRAM regions and bypass the chipset D_LCK (SMRAM D-lock) protection mechanism. This out-of-bounds write (CWE-787) allows code injection directly into System Management Mode memory. The attack requires KVM acceleration and privileged guest access; exploitation is not possible on systems with VAPIC disabled or guests using x2APIC/MSR-based TPR access mechanisms. Patches are expected from the QEMU project.

## Affected products

- QEMU QEMU <UNKNOWN>

## Timeline

- 2026-09-18: disclosed

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-81627](https://access.redhat.com/security/cve/CVE-2026-81627)

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