Executive brief
Xen, a popular open-source virtualization platform, contains a flaw in how it manages internal locks during guest management operations. An attacker with limited privileges on the system can exploit this to stall more important system tasks, potentially causing the entire host server to become unresponsive. This results in a denial-of-service condition that can disrupt all virtual machines running on the affected hardware.
Technical details
A vulnerability exists in Xen's domctl (domain control) operations when XSM/Flask is in use. The root cause is that the system-wide domctl lock is acquired before XSM permission checks are performed for certain operations. This allows a less-privileged entity (such as a domain controlling a particular guest or a Xenstore domain) to acquire the lock and hold it, effectively stalling more privileged entities or the control domain. This lack of fairness and improper ordering of operations can be leveraged to cause a Denial of Service (DoS) across the entire host. The issue affects Xen versions 3.3 and onwards. Patches are available via Xen Security Advisory XSA-492.
Affected products
- Xen Project Xen 3.3 and later
Timeline
- 2026-06-09: disclosed: Initial public release of XSA-492
- 2026-06-18: advisory: NVD publication date