CVE-2026-90420 nilfs2: fix infinite loop in nilfs_clean_segments()
A local attacker can cause a denial of service in the Linux kernel by triggering an infinite loop in the nilfs2 filesystem cleaner.
- 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-2026-90420?
CVE-2026-90420 is a denial of service vulnerability in Linux, published on 17 Sep 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:
nilfs2: fix infinite loop in nilfs_clean_segments()
syzbot reported a hung task in nilfs_transaction_begin(). This occurs because the cleaner ioctl falls into an infinite loop if nilfs_segctor_construct() repeatedly returns -EROFS (e.g. the device is remounted as read-only after an I/O error).
Currently in nilfs_clean_segments(), if err is non-zero, it logs the error and sleeps but doesn't abort when it encounters a terminal error like -EROFS. This causes the thread to loop forever.
Fix this by breaking out of the loop if nilfs_segctor_construct() returns -EROFS. This matches the behaviour in nilfs_segctor_write_out(), which also handles -EROFS.
Which versions are affected by CVE-2026-90420?
How do I fix CVE-2026-90420?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-90420 being exploited?
There is no known exploitation of CVE-2026-90420 in the wild and no public exploit code.
Sources
Also known as AZL-102339, BELL-CVE-2026-90420, DEBIAN-CVE-2026-90420, GHSA-fc9x-c3wj-jf8g, UBUNTU-CVE-2026-90420.