CVE-2025-40272 mm/secretmem: fix use-after-free race in fault handler
A race condition in the Linux kernel secret memory fault handler can cause a use-after-free, leading to a system crash.
- 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-2025-40272?
CVE-2025-40272 is a high-severity use after free vulnerability in Linux, published on 6 Dec 2025. 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/secretmem: fix use-after-free race in fault handler
When a page fault occurs in a secret memory file created with `memfd_secret(2)`, the kernel will allocate a new folio for it, mark the underlying page as not-present in the direct map, and add it to the file mapping.
If two tasks cause a fault in the same page concurrently, both could end up allocating a folio and removing the page from the direct map, but only one would succeed in adding the folio to the file mapping. The task that failed undoes the effects of its attempt by (a) freeing the folio again and (b) putting the page back into the direct map. However, by doing these two operations in this order, the page becomes available to the allocator again before it is placed back in the direct mapping.
If another task attempts to allocate the page between (a) and (b), and the kernel tries to access it via the direct map, it would result in a supervisor not-present page fault.
Fix the ordering to restore the direct map before the folio is freed.
Which versions are affected by CVE-2025-40272?
How do I fix CVE-2025-40272?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2025-40272 being exploited?
There is no known exploitation of CVE-2025-40272 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40272, DEBIAN-CVE-2025-40272, GHSA-cv75-hxcc-wfxg, ROOT-OS-DEBIAN-12-CVE-2025-40272, ROOT-OS-DEBIAN-13-CVE-2025-40272, ROOT-OS-UBUNTU-2204-CVE-2025-40272 and 2 more.