CVE-2025-21835 usb: gadget: f_midi: fix MIDI Streaming descriptor lengths
A Linux kernel USB gadget driver flaw leaks uninitialized stack memory to the host when MIDI port counts differ, requiring specific gadget configuration.
- 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-2025-21835?
CVE-2025-21835 is a medium-severity vulnerability in Linux kernel, published on 7 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:
usb: gadget: f_midi: fix MIDI Streaming descriptor lengths
While the MIDI jacks are configured correctly, and the MIDIStreaming endpoint descriptors are filled with the correct information, bNumEmbMIDIJack and bLength are set incorrectly in these descriptors.
This does not matter when the numbers of in and out ports are equal, but when they differ the host will receive broken descriptors with uninitialized stack memory leaking into the descriptor for whichever value is smaller.
The precise meaning of "in" and "out" in the port counts is not clearly defined and can be confusing. But elsewhere the driver consistently uses this to match the USB meaning of IN and OUT viewed from the host, so that "in" ports send data to the host and "out" ports receive data from it.
Which versions are affected by CVE-2025-21835?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21835?
Apply the vendor's patch.
Is CVE-2025-21835 being exploited?
There is no known exploitation of CVE-2025-21835 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-21835, DEBIAN-CVE-2025-21835, GHSA-2x4w-2j26-p5hx, ROOT-OS-UBUNTU-2404-CVE-2025-21835, UBUNTU-CVE-2025-21835.