---
id: CVE-2026-55781
title: NanaZip is the 7-Zip derivative intended for the modern Windows experience
summary: >-
  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 bo…
severity: none
cwe:
  - CWE-400
  - CWE-789
published: '2026-07-10'
updated: '2026-07-10'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-55781'
references:
  - url: >-
      https://github.com/M2Team/NanaZip/commit/6415b6bff70bc9c486b49cbbc1982724c67f8338
    label: security-advisories@github.com
  - url: 'https://github.com/M2Team/NanaZip/releases/tag/6.5.1749.0'
    label: security-advisories@github.com
  - url: 'https://github.com/M2Team/NanaZip/security/advisories/GHSA-m34h-jf84-m74h'
    label: security-advisories@github.com
tags:
  - nvd
  - exploit-available
epss: 0.00159
epssPercentile: 0.04304
ingestedAt: '2026-07-11T20:15:26.113Z'
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/yzy0okrkv1hngo0r/CVE-2026-55781-poc'
  checkedAt: '2026-09-25T08:21:03.549Z'
exploitAvailable: true
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.