DEBIAN-CVE-2026-99168: Debian/linux vulnerability
In the Linux kernel, the following vulnerability has been resolved: mshvvtl: Check per-CPU register page before mmap Register-page setup is optional for each CPU. If allocation or registration fails, mshvvtlconfigureregpage() warns and leaves that CPU's regpage NULL, but initial context setup continues successfully. Meanwhile, successful setup on another CPU sets the global mshvhasregpage flag. mshvvtlfault() checks this global flag before selecting the requested CPU's register page. With mixed setup results across online CPUs, the check passes even for a CPU with no register page, reaching getpage(NULL) when userspace faults in that mapping. Check the selected per-CPU register page before taking its reference and return VMFAULTSIGBUS if it is absent.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
In mshv_vtl_fault(), check the selected CPU's per-CPU register page before taking its reference; if the register page is absent, return VM_FAULT_SIGBUS.