CVE-2025-40203 listmount: don't call path_put() under namespace semaphore
A use-after-free vulnerability in the Linux kernel's listmount function allows attackers to potentially execute code or escalate privileges.
- 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-2025-40203?
CVE-2025-40203 is a high-severity use after free vulnerability in Linux, published on 12 Nov 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:
listmount: don't call path_put() under namespace semaphore
Massage listmount() and make sure we don't call path_put() under the namespace semaphore. If we put the last reference we're fscked.
Which versions are affected by CVE-2025-40203?
How do I fix CVE-2025-40203?
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-2025-40203 being exploited?
There is no known exploitation of CVE-2025-40203 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40203, DEBIAN-CVE-2025-40203, GHSA-9f95-mpr2-5ghw, ROOT-OS-DEBIAN-13-CVE-2025-40203, ROOT-OS-UBUNTU-2404-CVE-2025-40203, UBUNTU-CVE-2025-40203.