CVE-2025-71197 w1: therm: Fix off-by-one buffer overflow in alarms_store
An off-by-one buffer overflow in the Linux kernel w1 therm driver allows local attackers to potentially execute code or escalate privileges.
- 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-2025-71197?
CVE-2025-71197 is a memory corruption vulnerability in Linux, published on 4 Feb 2026. 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:
w1: therm: Fix off-by-one buffer overflow in alarms_store
The sysfs buffer passed to alarms_store() is allocated with 'size + 1' bytes and a NUL terminator is appended. However, the 'size' argument does not account for this extra byte. The original code then allocated 'size' bytes and used strcpy() to copy 'buf', which always writes one byte past the allocated buffer since strcpy() copies until the NUL terminator at index 'size'.
Fix this by parsing the 'buf' parameter directly using simple_strtoll() without allocating any intermediate memory or string copying. This removes the overflow while simplifying the code.
Which versions are affected by CVE-2025-71197?
How do I fix CVE-2025-71197?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2025-71197 being exploited?
There is no known exploitation of CVE-2025-71197 in the wild and no public exploit code.
Sources
Also known as AZL-77211, BELL-CVE-2025-71197, DEBIAN-CVE-2025-71197, GHSA-4c4g-c6q5-6cpq, ROOT-OS-UBUNTU-2204-CVE-2025-71197, ROOT-OS-UBUNTU-2404-CVE-2025-71197 and 1 more.