CVE-2025-68339 atm/fore200e: Fix possible data race in fore200e_open()
A race condition in the Linux kernel ATM fore200e driver allows concurrent access to shared bandwidth resources, potentially causing incorrect accounting and denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-68339?
CVE-2025-68339 is a vulnerability in Linux, published on 23 Dec 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:
atm/fore200e: Fix possible data race in fore200e_open()
Protect access to fore200e->available_cell_rate with rate_mtx lock in the error handling path of fore200e_open() to prevent a data race.
The field fore200e->available_cell_rate is a shared resource used to track available bandwidth. It is concurrently accessed by fore200e_open(), fore200e_close(), and fore200e_change_qos().
In fore200e_open(), the lock rate_mtx is correctly held when subtracting vcc->qos.txtp.max_pcr from available_cell_rate to reserve bandwidth. However, if the subsequent call to fore200e_activate_vcin() fails, the function restores the reserved bandwidth by adding back to available_cell_rate without holding the lock.
This introduces a race condition because available_cell_rate is a global device resource shared across all VCCs. If the error path in fore200e_open() executes concurrently with operations like fore200e_close() or fore200e_change_qos() on other VCCs, a read-modify-write race occurs.
Specifically, the error path reads the rate without the lock. If another CPU acquires the lock and modifies the rate (e.g., releasing bandwidth in fore200e_close()) between this read and the subsequent write, the error path will overwrite the concurrent update with a stale value. This results in incorrect bandwidth accounting.
Which versions are affected by CVE-2025-68339?
How do I fix CVE-2025-68339?
Apply the vendor's patch.
Is CVE-2025-68339 being exploited?
There is no known exploitation of CVE-2025-68339 in the wild and no public exploit code.
Sources
Also known as AZL-72980, BELL-CVE-2025-68339, DEBIAN-CVE-2025-68339, GHSA-p5pr-v4m5-r2vj, ROOT-OS-DEBIAN-12-CVE-2025-68339, ROOT-OS-DEBIAN-13-CVE-2025-68339 and 3 more.