CVE-2025-40198 ext4: avoid potential buffer over-read in parse_apply_sb_mount_options()
A buffer over-read in the Linux kernel ext4 filesystem allows attackers to cause denial of service or disclose sensitive memory information.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2025-40198?
CVE-2025-40198 is a high-severity memory corruption vulnerability in Linux, published on 12 Nov 2025. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ext4: avoid potential buffer over-read in parse_apply_sb_mount_options()
Unlike other strings in the ext4 superblock, we rely on tune2fs to make sure s_mount_opts is NUL terminated. Harden parse_apply_sb_mount_options() by treating s_mount_opts as a potential __nonstring.
Which versions are affected by CVE-2025-40198?
How do I fix CVE-2025-40198?
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-2025-40198 being exploited?
There is no known exploitation of CVE-2025-40198 in the wild and no public exploit code.
Sources
Also known as AZL-70067, BELL-CVE-2025-40198, DEBIAN-CVE-2025-40198, GHSA-w7vv-57v2-cqgf, ROOT-OS-DEBIAN-11-CVE-2025-40198, ROOT-OS-UBUNTU-2204-CVE-2025-40198 and 2 more.