CVE-2026-55392 NILFS utilities - Undefined Behavior and Out-of-Memory via Unvalidated s_log_block_size
Attackers can crash NILFS2 utilities by providing crafted filesystem images with invalid block sizes, causing out-of-memory errors or undefined behavior.
- 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-2026-55392?
CVE-2026-55392 is a medium-severity denial of service vulnerability in nilfs-dev nilfs-utils, published on 18 Jun 2026. 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
NILFS utilities through 2.3.0, fixed in commit 26efb5d, nilfs_sb_is_valid() function fails to validate s_log_block_size field in NILFS2 superblock before bit-shift operations. Attackers supplying crafted NILFS2 images trigger undefined behavior through oversized shifts or out-of-memory conditions, crashing tools like nilfs-tune and dumpseg.
Weakness: CWE-1284
Which versions are affected by CVE-2026-55392?
Linux distribution packages (2)
nilfs-utils openSUSE:Leap 16.0 | All versions | 2.2.9-bp160.2.1 |
nilfs-utils openSUSE:Tumbleweed | All versions | 2.3.1-1.1 |
How do I fix CVE-2026-55392?
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-2026-55392 being exploited?
There is no known exploitation of CVE-2026-55392 in the wild and no public exploit code.
Sources
Also known as AZL-90200, DEBIAN-CVE-2026-55392, GHSA-f559-vgh2-9hj6, MGASA-2026-0280, OESA-2026-2795, OESA-2026-2796 and 5 more.