CVE-2026-55781lowCWE-400CWE-789

CVE-2026-55781: low-severity vulnerability in M2Team NanaZip

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

Published

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28Vexday Risk Score

No sign of exploitation. It has a public proof of concept.

ssvc Attendcvss 2.4epss 0.2%
from disclosure to weapon69 days
Published on NVDJul 10
1st PoC+69d
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.
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
Affected products
M2Team · NanaZip
⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
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