CVE-2025-39975 smb: client: fix wrong index reference in smb2_compound_op()
A wrong index reference in the Linux kernel SMB client can cause out-of-bounds memory accesses, potentially leading to code execution or system crashes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39975?
CVE-2025-39975 is a critical memory corruption vulnerability in Linux, published on 15 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:
smb: client: fix wrong index reference in smb2_compound_op()
In smb2_compound_op(), the loop that processes each command's response uses wrong indices when accessing response bufferes.
This incorrect indexing leads to improper handling of command results. Also, if incorrectly computed index is greather than or equal to MAX_COMPOUND, it can cause out-of-bounds accesses.
Which versions are affected by CVE-2025-39975?
How do I fix CVE-2025-39975?
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-2025-39975 being exploited?
There is no known exploitation of CVE-2025-39975 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-39975, DEBIAN-CVE-2025-39975, GHSA-cm9p-f4x4-35gj, ROOT-OS-DEBIAN-13-CVE-2025-39975, UBUNTU-CVE-2025-39975.