Xen VMX VMEntry resource consumption

Summaryinfo

A vulnerability was found in Xen. It has been classified as problematic. This affects an unknown part of the component VMX VMEntry. This manipulation causes resource consumption. This vulnerability appears as CVE-2026-79611. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability has been found in Xen (unknown version) and classified as problematic. Affected by this vulnerability is an unknown code block of the component VMX VMEntry. The manipulation with an unknown input leads to a resource consumption vulnerability. The CWE definition for the vulnerability is CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. As an impact it is known to affect availability. The summary by CVE is:

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.

The advisory is shared at xenbits.xenproject.org. This vulnerability is known as CVE-2026-79611 since 08/25/2026. The exploitation appears to be easy. The attack can be launched remotely. Additional levels of successful authentication are necessary for exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/13/2026). MITRE ATT&CK project uses the attack technique T1499 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Virtualization Software

Name

• Xen

License

• open-source

CPE 2.3info

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CPE 2.2info

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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