What’s Vulnerable › Vulnerabilities

CVE-2026-55781: NanaZip: Unbounded memory allocation (DoS) in NanaZip UFS parser via unvalidated fs_bsize/fs_fsize superblock fields

• Severity: low (CVSS 2.4 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-10 · updated 2026-10-25
• Weakness: CWE-400

Description

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 fs_fsize 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 products

• M2Team NanaZip: before 6.5.1749.0

References

• https://github.com/M2Team/NanaZip/commit/6415b6bff70bc9c486b49cbbc1982724c67f8338
• https://github.com/M2Team/NanaZip/releases/tag/6.5.1749.0
• https://github.com/M2Team/NanaZip/security/advisories/GHSA-m34h-jf84-m74h

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