CVE-2026-79611
Published Oct 13, 2026
Modified Oct 13, 2026
Description
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.
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References
Frequently Asked Questions
What is CVE-2026-79611? +
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.
How do I check if I'm vulnerable to CVE-2026-79611? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.