CVE-2025-40253 s390/ctcm: Fix double-kfree
A double-free vulnerability in the s390/ctcm Linux kernel driver allows attackers to cause a denial of service or potentially execute arbitrary code.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-40253?
CVE-2025-40253 is a high-severity use after free vulnerability in Linux, published on 4 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:
s390/ctcm: Fix double-kfree
The function 'mpc_rcvd_sweep_req(mpcginfo)' is called conditionally from function 'ctcmpc_unpack_skb'. It frees passed mpcginfo. After that a call to function 'kfree' in function 'ctcmpc_unpack_skb' frees it again.
Remove 'kfree' call in function 'mpc_rcvd_sweep_req(mpcginfo)'.
Bug detected by the clang static analyzer.
Which versions are affected by CVE-2025-40253?
How do I fix CVE-2025-40253?
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-2025-40253 being exploited?
There is no known exploitation of CVE-2025-40253 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40253, DEBIAN-CVE-2025-40253, GHSA-c7q5-6cjw-qjwq, ROOT-OS-DEBIAN-11-CVE-2025-40253, ROOT-OS-UBUNTU-2204-CVE-2025-40253, ROOT-OS-UBUNTU-2404-CVE-2025-40253 and 1 more.