CVE-2025-39926 genetlink: fix genl_bind() invoking bind() after -EPERM
Unauthorized users can trigger bind callbacks in the Linux kernel genetlink subsystem despite permission checks failing, bypassing intended access controls.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39926?
CVE-2025-39926 is a medium-severity missing authorization vulnerability in Linux kernel, published on 1 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
genetlink: fix genl_bind() invoking bind() after -EPERM
Per family bind/unbind callbacks were introduced to allow families to track multicast group consumer presence, e.g. to start or stop producing events depending on listeners.
However, in genl_bind() the bind() callback was invoked even if capability checks failed and ret was set to -EPERM. This means that callbacks could run on behalf of unauthorized callers while the syscall still returned failure to user space.
Fix this by only invoking bind() after "if (ret) break;" check i.e. after permission checks have succeeded.
Which versions are affected by CVE-2025-39926?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-39926?
Apply the vendor's patch.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2025-39926 being exploited?
There is no known exploitation of CVE-2025-39926 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-39926, DEBIAN-CVE-2025-39926, GHSA-f9wm-ppg2-pc92, UBUNTU-CVE-2025-39926.