CVE-2025-21915 cdx: Fix possible UAF error in driver_override_show()
A race condition in the Linux kernel CDX bus driver allows unprivileged users to trigger a use-after-free, potentially leaking kernel addresses or causing a crash.
- 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-2025-21915?
CVE-2025-21915 is a high-severity use after free 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:
cdx: Fix possible UAF error in driver_override_show()
Fixed a possible UAF problem in driver_override_show() in drivers/cdx/cdx.c
This function driver_override_show() is part of DEVICE_ATTR_RW, which includes both driver_override_show() and driver_override_store(). These functions can be executed concurrently in sysfs.
The driver_override_store() function uses driver_set_override() to update the driver_override value, and driver_set_override() internally locks the device (device_lock(dev)). If driver_override_show() reads cdx_dev->driver_override without locking, it could potentially access a freed pointer if driver_override_store() frees the string concurrently. This could lead to printing a kernel address, which is a security risk since DEVICE_ATTR can be read by all users.
Additionally, a similar pattern is used in drivers/amba/bus.c, as well as many other bus drivers, where device_lock() is taken in the show function, and it has been working without issues.
This potential bug was detected by our experimental static analysis tool, which analyzes locking APIs and paired functions to identify data races and atomicity violations.
Weakness: CWE-416
Which versions are affected by CVE-2025-21915?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21915?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2025-21915 being exploited?
There is no known exploitation of CVE-2025-21915 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-21915, DEBIAN-CVE-2025-21915, GHSA-4v94-f8pq-mj8v, ROOT-OS-UBUNTU-2204-CVE-2025-21915, ROOT-OS-UBUNTU-2404-CVE-2025-21915, UBUNTU-CVE-2025-21915.