CVE-2026-99168 mshv_vtl: Check per-CPU register page before mmap
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99168?
CVE-2026-99168 is a vulnerability in Linux, published on 28 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
mshv_vtl: Check per-CPU register page before mmap
Register-page setup is optional for each CPU. If allocation or registration fails, mshv_vtl_configure_reg_page() warns and leaves that CPU's reg_page NULL, but initial context setup continues successfully. Meanwhile, successful setup on another CPU sets the global mshv_has_reg_page flag.
mshv_vtl_fault() 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 get_page(NULL) when userspace faults in that mapping.
Check the selected per-CPU register page before taking its reference and return VM_FAULT_SIGBUS if it is absent.
Which versions are affected by CVE-2026-99168?
How do I fix CVE-2026-99168?
Upgrade to a fixed version.
Is CVE-2026-99168 being exploited?
There is no known exploitation of CVE-2026-99168 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-99168, GHSA-3wc5-v6vv-97qx, UBUNTU-CVE-2026-99168.