PatchTheCVECVE-2026-55781: NanaZip is the 7-Zip derivative intended for the modern Windows experience
CVE-2026-55781 is a low-severity flaw (CVSS 2.4) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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-
Why this priority
- No elevated risk signals yet
No fix is published yet: follow the downgrade or mitigation steps.
Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-55781?
No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.
Is CVE-2026-55781 being exploited?
CVE-2026-55781 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-55781 affect?
CVE-2026-55781 affects affected software. Severity is low (CVSS 2.4). 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
How urgent is CVE-2026-55781?
Priority 10/100. No elevated risk signals yet.
Software pages
Windows vulnerabilities · 7-Zip vulnerabilities