CVE-2026-79611
VMX: VMentry failure with branch tracing and blocked states
CVSS Score
0.0
EPSS Score
0.0%
EPSS Percentile
0th
For XSA-308 logic was introduced, as VMX VMEntry checks do not like the exact combination of state which occurs when #DB in intercepted, Single Stepping is active, and blocked by STI/MovSS is active, despite this being a legitimate state to be in. The resulting VMEntry failure is fatal to the guest. Sadly there is another special sub-case of the above, with branch tracing enabled. In that case the prior adjustment would still cause a VMentry failure, as before fatal to the guest.
| Vendor | xen |
| Product | xen |
| Published | Oct 13, 2026 |
| Last Updated | Oct 13, 2026 |
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Affected Versions
Xen / Xen
All versions affected References
Credits
This issue was discovered by Claude Opus and diagnosed as a security issue
by Teddy Astie of Vates.