CVE-2025-40286 smb/server: fix possible memory leak in smb2_read()
A memory leak in the Linux kernel's SMB server allows remote attackers to cause a denial of service by triggering read failures.
- 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-2025-40286?
CVE-2025-40286 is a denial of service vulnerability in Linux, published on 6 Dec 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:
smb/server: fix possible memory leak in smb2_read()
Memory leak occurs when ksmbd_vfs_read() fails. Fix this by adding the missing kvfree().
Which versions are affected by CVE-2025-40286?
How do I fix CVE-2025-40286?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-40286 being exploited?
There is no known exploitation of CVE-2025-40286 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40286, DEBIAN-CVE-2025-40286, GHSA-4fg7-4778-957g, ROOT-OS-DEBIAN-12-CVE-2025-40286, ROOT-OS-DEBIAN-13-CVE-2025-40286, ROOT-OS-UBUNTU-2204-CVE-2025-40286 and 2 more.