CVE-2026-74600 mm/page_table_check: skip special zero mappings
An unprivileged local user can trigger a kernel crash by overflowing file_map_count via special zero mappings in the page table checker.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74600?
CVE-2026-74600 is a denial of service vulnerability in Linux, published on 22 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
mm/page_table_check: skip special zero mappings
page_table_check_set() and page_table_check_clear() account mappings based on PageAnon(). Shared zero-page PTEs and huge zero PMDs are special mappings, but page_table_check can still account them as file-backed pages.
An unprivileged process can populate enough zero mappings to overflow file_map_count and hit the existing BUG_ON(). The PTE path can do this with the shared zero page, and the PMD path can do the same with huge zero mappings.
Skip special zero mappings in the user page-table accounting paths. Keep the PTE-side pte_special() check, and identify huge zero PMDs from the mapped folio instead of pmd_special(). That covers architectures where pmd_special() is a no-op without adding huge_zero_pfn checks to the generic counter helpers.
Which versions are affected by CVE-2026-74600?
How do I fix CVE-2026-74600?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-74600 being exploited?
There is no known exploitation of CVE-2026-74600 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-74600, DEBIAN-CVE-2026-74600, GHSA-mr2c-gwqw-3x39, UBUNTU-CVE-2026-74600.