CVE-2025-21853 bpf: avoid holding freeze_mutex during mmap operation
A race condition in the Linux kernel BPF subsystem can cause deadlocks during memory mapping operations, leading to system 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-2025-21853?
CVE-2025-21853 is a medium-severity vulnerability in Linux kernel, published on 12 Mar 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:
bpf: avoid holding freeze_mutex during mmap operation
We use map->freeze_mutex to prevent races between map_freeze() and memory mapping BPF map contents with writable permissions. The way we naively do this means we'll hold freeze_mutex for entire duration of all the mm and VMA manipulations, which is completely unnecessary. This can potentially also lead to deadlocks, as reported by syzbot in [0].
So, instead, hold freeze_mutex only during writeability checks, bump (proactively) "write active" count for the map, unlock the mutex and proceed with mmap logic. And only if something went wrong during mmap logic, then undo that "write active" counter increment.
[0] https://lore.kernel.org/bpf/[email protected]/
Which versions are affected by CVE-2025-21853?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21853?
Apply the vendor's patch.
Is CVE-2025-21853 being exploited?
There is no known exploitation of CVE-2025-21853 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-58487, AZL-58536, BELL-CVE-2025-21853, DEBIAN-CVE-2025-21853, GHSA-xgr9-crfp-4qg4, ROOT-OS-UBUNTU-2204-CVE-2025-21853 and 2 more.