Varstored
Monthly
Guest-to-host privilege escalation in varstored, the Xapi (XenServer/XCP-ng/Citrix Hypervisor) toolstack daemon that services UEFI variable requests for VMs, allows a malicious guest to corrupt control flow in the host-side process. Missing compiler barriers on a buffer shared with in-guest OVMF create a time-of-check/time-of-use race (CWE-367) that, in default builds, lets the attacker control an index into a jump table - yielding attacker-influenced execution in the toolstack. Tracked as Xen Security Advisory XSA-478 with a CVSS 4.0 base score of 9.4; no public exploit identified at time of analysis and not listed in CISA KEV.
Guest-to-host privilege escalation in varstored, the Xapi (XenServer/XCP-ng/Citrix Hypervisor) toolstack daemon that services UEFI variable requests for VMs, allows a malicious guest to corrupt control flow in the host-side process. Missing compiler barriers on a buffer shared with in-guest OVMF create a time-of-check/time-of-use race (CWE-367) that, in default builds, lets the attacker control an index into a jump table - yielding attacker-influenced execution in the toolstack. Tracked as Xen Security Advisory XSA-478 with a CVSS 4.0 base score of 9.4; no public exploit identified at time of analysis and not listed in CISA KEV.