CVE-2026-55781: NanaZip: Unbounded memory allocation (DoS) in NanaZip UFS parser via unvalidated fs_bsize/fs_fsize superblock fields
NanaZip is the 7-Zip derivative intended for the modern Windows experience. Prior to 6.5.1749.0, NanaZip's UFS and FFS image handler in NanaZip.Codecs.Archive.Ufs.cpp validates the superblock block size only against the MINBSIZE lower bound and does not validate the fsfsize fragment size, allowing attacker-controlled 32-bit fields to flow into indirect-block, directory, and extraction buffer allocations. A tiny crafted UFS image can force multi-gigabyte allocations during open or extraction, causing memory exhaustion or process termination. This issue is fixed in version 6.5.1749.0.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
NanaZipto a version that resolves this vulnerability.Fixed in 6.5.1749.0
Event History
Frequently Asked Questions
What is the severity of CVE-2026-55781?
The severity of CVE-2026-55781 is low with a CVSS score of 4.0.
How do I fix CVE-2026-55781?
To fix CVE-2026-55781, update NanaZip to version 6.5.1749.0 or later.
What type of vulnerability is CVE-2026-55781?
CVE-2026-55781 is an unbounded memory allocation vulnerability that can lead to a denial of service (DoS).
Which component is affected by CVE-2026-55781?
CVE-2026-55781 affects the UFS and FFS image handler in NanaZip.
What are the potential impacts of CVE-2026-55781?
The potential impacts of CVE-2026-55781 include denial of service due to unvalidated superblock fields in file handling.