Vulnerability · Published Jun 18, 2026 · Assigned by VulnCheck
CVE-2026-55392NILFS utilities - Undefined Behavior and Out-of-Memory via Unvalidated s_log_block_size
Medium 5.5
In plain English
A medium-severity security flaw in nilfs-utils from nilfs-dev. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 4% of all known vulnerabilities).
Severity (CVSS 3.1)5.5Medium
Exploit odds (30 days)0.2%top 95.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | nilfs-tools | no fix listed | DEBIAN-CVE-2026-55392 |
| Debian:13 | nilfs-tools | no fix listed | DEBIAN-CVE-2026-55392 |
| Debian:14 | nilfs-tools | no fix listed | DEBIAN-CVE-2026-55392 |
| Ubuntu:22.04:LTS | nilfs-tools | no fix listed | UBUNTU-CVE-2026-55392 |
| Ubuntu:24.04:LTS | nilfs-tools | no fix listed | UBUNTU-CVE-2026-55392 |
| Ubuntu:25.10 | nilfs-tools | no fix listed | UBUNTU-CVE-2026-55392 |
| Ubuntu:26.04:LTS | nilfs-tools | no fix listed | UBUNTU-CVE-2026-55392 |
| Ubuntu:26.10 | nilfs-tools | no fix listed | UBUNTU-CVE-2026-55392 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| nilfs-dev | nilfs-utils | 0 – through 2.3.0 |
Weakness: CWE-1284 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
References
- Pull Request issue-tracking
- Patch Commit patch