CVE-2026-42488 Details

A vulnerability in Xen Project's handling of shadow paging can lead to privilege escalation, denial-of-service (DoS) affecting the entire host, and information leaks. This issue arises because certain error paths in shadow paging switch the page tables without updating the reference to the currently running vCPU. As a result, there is a mismatch between the loaded page tables and the mapcache metadata, which can corrupt the mapcache. This vulnerability affects Xen versions 4.15 and onwards, specifically on x86 systems with 64-bit PV guests running in shadow mode, such as during guest migration or as a workaround for the L1TF vulnerability.

Users can apply the patch provided in the Xen Security Advisory XSA-494 to address this vulnerability. Patches are available for Xen 4.17.x, 4.18.x, 4.20.x - 4.19.x, and 4.21.x. For versions 4.15 and onwards, the vulnerability can be mitigated by running only HVM or PVH guests, or by using the PV shim for PV guests.