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

Quick assessment

Affected
M2Team NanaZip
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

m2team nanazip是m2team团队开源的一个压缩软件。 M2Team NanaZip 6.5.1749.0之前版本存在资源管理错误漏洞，该漏洞源于对UFS和FFS图像处理程序中的超块块大小验证不完整且未验证fs_fsize片段大小，导致攻击者控制的32位字段流入间接块、目录和提取缓冲区分配。特制的UFS镜像在打开或提取过程中可能导致内存耗尽或进程终止。

AI Predicted 8.1 Difficulty: Moderate EPSS 0.16% · P4

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 1

VendorProduct Version RangeStatus
M2Team NanaZip < 6.5.1749.0 affected
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I. Basic Information for CVE-2026-55781

Vulnerability Information
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Vulnerability Title
NanaZip: Unbounded memory allocation (DoS) in NanaZip UFS parser via unvalidated fs_bsize/fs_fsize superblock fields
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
M2Team NanaZip 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
m2team nanazip是m2team团队开源的一个压缩软件。 M2Team NanaZip 6.5.1749.0之前版本存在资源管理错误漏洞，该漏洞源于对UFS和FFS图像处理程序中的超块块大小验证不完整且未验证fs_fsize片段大小，导致攻击者控制的32位字段流入间接块、目录和提取缓冲区分配。特制的UFS镜像在打开或提取过程中可能导致内存耗尽或进程终止。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
M2Team NanaZip < 6.5.1749.0 -

II. Public POCs for CVE-2026-55781

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III. Intelligence Information for CVE-2026-55781

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Patches & Fixes for CVE-2026-55781 (1)

Vendor Advisories for CVE-2026-55781 (1)

Vendor Pages for CVE-2026-55781 (1)

Same Patch Batch · M2Team · 2026-07-10 · 4 CVEs total

CVE-2026-55780 NanaZip: Uncaught exception / unbounded allocation in NanaZip .NET single-file Extract() v
CVE-2026-55783 NanaZip: NULL pointer dereference in Extract() of all seven NanaZip custom archive handler
CVE-2026-55782 NanaZip: Unbounded memory allocation (DoS) in NanaZip WebAssembly parser via attacker-cont

IV. Related Vulnerabilities

Same product: NanaZip
Same vendor: M2Team
Same weakness: CWE-400

V. Comments for CVE-2026-55781

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