CVE-2025-21909 wifi: nl80211: reject cooked mode if it is set along with other flags
A local attacker can trigger a kernel warning and potential denial of service by setting conflicting Wi-Fi monitor flags simultaneously.
- 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-2025-21909?
CVE-2025-21909 is a medium-severity vulnerability in Linux kernel, published on 1 Apr 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:
wifi: nl80211: reject cooked mode if it is set along with other flags
It is possible to set both MONITOR_FLAG_COOK_FRAMES and MONITOR_FLAG_ACTIVE flags simultaneously on the same monitor interface from the userspace. This causes a sub-interface to be created with no IEEE80211_SDATA_IN_DRIVER bit set because the monitor interface is in the cooked state and it takes precedence over all other states. When the interface is then being deleted the kernel calls WARN_ONCE() from check_sdata_in_driver() because of missing that bit.
Fix this by rejecting MONITOR_FLAG_COOK_FRAMES if it is set along with other flags.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Weakness: CWE-362
Which versions are affected by CVE-2025-21909?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21909?
Apply the vendor's patch.
Is CVE-2025-21909 being exploited?
There is no known exploitation of CVE-2025-21909 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-21909, DEBIAN-CVE-2025-21909, GHSA-4m83-xp7j-q4j9, ROOT-OS-UBUNTU-2404-CVE-2025-21909, UBUNTU-CVE-2025-21909.