CVE-2025-39943 ksmbd: smbdirect: validate data_offset and data_length field of smb_direct_data_transfer
An out-of-bounds memory access in the Linux kernel ksmbd module allows attackers to potentially execute code or cause a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39943?
CVE-2025-39943 is a critical memory corruption vulnerability in Linux kernel, published on 4 Oct 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: smbdirect: validate data_offset and data_length field of smb_direct_data_transfer
If data_offset and data_length of smb_direct_data_transfer struct are invalid, out of bounds issue could happen. This patch validate data_offset and data_length field in recv_done.
Weakness: CWE-125
Which versions are affected by CVE-2025-39943?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-39943?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2025-39943 being exploited?
There is no known exploitation of CVE-2025-39943 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-39943, DEBIAN-CVE-2025-39943, GHSA-xw7x-gch6-cpx7, ROOT-OS-DEBIAN-12-CVE-2025-39943, ROOT-OS-DEBIAN-13-CVE-2025-39943, ROOT-OS-UBUNTU-2204-CVE-2025-39943 and 2 more.