CVE-2025-21955 ksmbd: prevent connection release during oplock break notification
A use-after-free vulnerability in the Linux kernel ksmbd module allows attackers to cause denial of service or execute arbitrary code.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-21955?
CVE-2025-21955 is a high-severity use after free vulnerability in Linux kernel, published on 1 Apr 2025. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: prevent connection release during oplock break notification
ksmbd_work could be freed when after connection release. Increment r_count of ksmbd_conn to indicate that requests are not finished yet and to not release the connection.
Which versions are affected by CVE-2025-21955?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21955?
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-2025-21955 being exploited?
There is no known exploitation of CVE-2025-21955 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-21955, DEBIAN-CVE-2025-21955, GHSA-p2c4-6w6j-w378, ROOT-OS-DEBIAN-12-CVE-2025-21955, ROOT-OS-UBUNTU-2204-CVE-2025-21955, ROOT-OS-UBUNTU-2404-CVE-2025-21955 and 1 more.