CVE-2025-39942 ksmbd: smbdirect: verify remaining_data_length respects max_fragmented_recv_size
A missing validation in the Linux kernel's ksmbd SMB Direct implementation allows remote attackers to cause a denial of service via crafted packets.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39942?
CVE-2025-39942 is a high-severity denial of service 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: verify remaining_data_length respects max_fragmented_recv_size
This is inspired by the check for data_offset + data_length.
Which versions are affected by CVE-2025-39942?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-39942?
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-2025-39942 being exploited?
There is no known exploitation of CVE-2025-39942 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-68139, AZL-75336, BELL-CVE-2025-39942, DEBIAN-CVE-2025-39942, GHSA-m5q9-73x5-pf78, ROOT-OS-DEBIAN-12-CVE-2025-39942 and 4 more.