# CVE-2026-79602: Xen improper HVM emulation return code handling

Source: https://junglewise.ai/threats/cve-2026-79602-xen-improper-hvm-emulation-return-code-handling  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-08. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-79602 · Severity: high · CVSS 8.8 · Published 2026-09-08

Xen is a virtualization platform that runs multiple isolated operating systems on a single physical host. A flaw in how Xen handles PCI device passthrough to virtual machines allows an unprivileged guest to crash the entire host. An attacker with control over a guest virtual machine could exploit this to cause a complete denial of service to all running guests and the host itself.

## Quick answers

**Is CVE-2026-79602 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-79602 being exploited in the wild.

**How severe is CVE-2026-79602?** High severity, with a CVSS score of 8.8, published 8 September 2026.

**Which products and versions are affected?** Xen Xen 4.6 and later.

**Is there a fix for CVE-2026-79602?** A patch was published on 2026-09-08: Patch xsa510.patch available Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-79602 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-79602?** Check whether anything you run is named in the advisory. 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

This vulnerability is a logic error in x86 HVM emulation return code handling within Xen. When a PCI device with at least one BAR (Base Address Register) in IO port space is passed through to an HVM guest, the guest can trigger a BUG() exception in the hypervisor via improper emulation return code processing. The attack is triggered from unprivileged guest context and requires the guest to have a PCI device with IO BARs assigned. Exploitation results in a host-level denial of service affecting all guests. A patch is available via XSA-510; Xen versions 4.6 and later on x86 systems are vulnerable (Arm systems are unaffected).

## Affected products

- Xen Xen 4.6 and later

## Timeline

- 2026-09-08: disclosed
- 2026-09-08: patched: Patch xsa510.patch available

## References

- [https://xenbits.xenproject.org/xsa/advisory-510.html](https://xenbits.xenproject.org/xsa/advisory-510.html)
- [http://www.openwall.com/lists/oss-security/2026/09/08/7](http://www.openwall.com/lists/oss-security/2026/09/08/7)