VM Entry Failure in Xen Hypervisor Under Specific Conditions
CVE-2026-79611

Currently unrated

Key Information:

Vendor: Xen Project
Status: Xen Project
Vendor: CVE Published:; 13 October 2026

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What is CVE-2026-79611?

A vulnerability in the Xen Hypervisor can cause VM entry failures under specific conditions, including when the #DB (debug exception) is intercepted, single stepping is active, and certain blocking mechanisms (STI/MovSS) are engaged. This situation results in a fatal state for the guest virtual machine, compromising its operational integrity. Moreover, an additional hazard presents itself when branch tracing is enabled, exacerbating the VM entry failure and leading to further complications for guest VMs. As a result, administrators must be vigilant and ensure appropriate mitigations are in place.

Affected Version(s)

Xen consult Xen advisory XSA-518

References

https://xenbits.xenproject.org/xsa/advisory-518.html

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Timeline

Vulnerability published
Oct 13, 2026
Vulnerability Reserved
Aug 25, 2026

Credit

This issue was discovered by Claude Opus and diagnosed as a security issue by Teddy Astie of Vates.

CVE-2026-79611 Data

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