CVE-2026-72025 s390/monwriter: Reject buffer reuse with different data length
A local attacker with access to the monwriter device can trigger memory corruption by changing data lengths, potentially leading to privilege escalation.
- 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-2026-72025?
CVE-2026-72025 is a memory corruption vulnerability in Linux, published on 15 Aug 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:
s390/monwriter: Reject buffer reuse with different data length
When data buffers are reused, e.g. for interval sample records, the first record determines the data length, and the size of the buffer for user copy. Current monwriter code does not check if the data length was changed for subsequent records, which also would never happen for valid user programs.
However, a malicious user could change the data length, resulting in out of bounds user copy to the kernel buffer, and memory corruption. By default, the monwriter misc device is created with root-only permissions, so practical impact is typically low.
Fix this by checking for changed data length and rejecting such records.
Which versions are affected by CVE-2026-72025?
How do I fix CVE-2026-72025?
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-2026-72025 being exploited?
There is no known exploitation of CVE-2026-72025 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72025, DEBIAN-CVE-2026-72025, GHSA-p5g5-p29w-rcw3, UBUNTU-CVE-2026-72025.