Executive brief
A vulnerability exists in the Xen hypervisor, which is software used to run multiple virtual machines on a single physical server. An attacker controlling a virtual machine could exploit a flaw in how the system manages memory sharing to gain full control over the host server. This could lead to the theft of data from other customers, a total system shutdown, or unauthorized access to the underlying infrastructure.
Technical details
A race condition exists in the Xen grant table implementation when switching between version 2 and version 1 (CVE-2026-62436). The vulnerability occurs because the code drops and re-acquires the grant table lock, incorrectly assuming that table properties (such as status frames) remain constant during the unlocked window. An unprivileged multi-vCPU x86 guest can exploit this timing window to trigger memory corruption or logic errors. This can result in guest-to-host privilege escalation, information disclosure, or a hypervisor crash. The issue affects all Xen versions from 4.0 onwards, specifically on x86 systems where grant table v2 is enabled.
Affected products
- Xen Project Xen 4.0 and newer
Timeline
- 2026-07-28: disclosed: Public release of XSA-501
- 2026-07-28: patched