CVE-2025-38509 wifi: mac80211: reject VHT opmode for unsupported channel widths
A missing validation in the Linux kernel Wi-Fi subsystem allows malformed VHT notifications to trigger a kernel warning, potentially causing a 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-2025-38509?
CVE-2025-38509 is a medium-severity denial of service vulnerability in Linux kernel, published on 16 Aug 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: mac80211: reject VHT opmode for unsupported channel widths
VHT operating mode notifications are not defined for channel widths below 20 MHz. In particular, 5 MHz and 10 MHz are not valid under the VHT specification and must be rejected.
Without this check, malformed notifications using these widths may reach ieee80211_chan_width_to_rx_bw(), leading to a WARN_ON due to invalid input. This issue was reported by syzbot.
Reject these unsupported widths early in sta_link_apply_parameters() when opmode_notif is used. The accepted set includes 20, 40, 80, 160, and 80+80 MHz, which are valid for VHT. While 320 MHz is not defined for VHT, it is allowed to avoid rejecting HE or EHT clients that may still send a VHT opmode notification.
Which versions are affected by CVE-2025-38509?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-38509?
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-2025-38509 being exploited?
There is no known exploitation of CVE-2025-38509 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-38509, GHSA-2chp-rwm6-cjcw, UBUNTU-CVE-2025-38509.