Executive brief
NanaZip is an open-source file archiver used to compress and decompress various file formats. A vulnerability in how it handles specific filesystem images (UFS/UFS2) allows an attacker to crash the application by providing a specially crafted file. While this does not lead to data theft or unauthorized access, it results in a denial-of-service where the software stops responding or closes unexpectedly when the malicious file is opened.
Technical details
An integer divide-by-zero vulnerability exists in the UFS/UFS2 filesystem image parser within NanaZip. The flaw is located in the GetInodeOffset function in NanaZip.Codecs.Archive.Ufs.cpp, where the superblock field 'fs_ipg' (inodes per cylinder group) is read from the disk and used as a divisor without validation. If an attacker provides a crafted UFS image with 'fs_ipg' set to zero, the application triggers a hardware divide-by-zero exception (x86 #DE), leading to an immediate process crash. This occurs during the archive opening phase (IInArchive::Open) before user interaction beyond selecting the file. The issue is fixed in version 6.0.1698.0.
Affected products
- M2Team NanaZip 5.0.1252.0 to before 6.0.1698.0
Timeline
- 2026-04-27: advisory: GitHub Security Advisory published by M2Team
- 2026-05-12: disclosed: CVE-2026-42443 published to NVD