CVE-2025-21666 vsock: prevent null-ptr-deref in vsock_*[has_data|has_space]
A null pointer dereference in the Linux kernel vsock subsystem can cause a system crash, requiring a kernel patch to prevent denial of service.
- 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-2025-21666?
CVE-2025-21666 is a medium-severity vulnerability in Linux kernel, published on 31 Jan 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:
vsock: prevent null-ptr-deref in vsock_*[has_data|has_space]
Recent reports have shown how we sometimes call vsock_*_has_data() when a vsock socket has been de-assigned from a transport (see attached links), but we shouldn't.
Previous commits should have solved the real problems, but we may have more in the future, so to avoid null-ptr-deref, we can return 0 (no space, no data available) but with a warning.
This way the code should continue to run in a nearly consistent state and have a warning that allows us to debug future problems.
Weakness: CWE-476
Which versions are affected by CVE-2025-21666?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21666?
Apply the vendor's patch.
Is CVE-2025-21666 being exploited?
There is no known exploitation of CVE-2025-21666 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-56279, AZL-56337, BELL-CVE-2025-21666, DEBIAN-CVE-2025-21666, GHSA-p6f8-9m89-hwvw, UBUNTU-CVE-2025-21666.