# CVE-2026-55782: M2Team NanaZip uncontrolled memory allocation in WebAssembly handler

Source: https://junglewise.ai/threats/cve-2026-55782-m2team-nanazip-uncontrolled-memory-allocation-in-webassembly  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-10. Updated: 2026-07-10  
License: CC BY 4.0 with a link back

CVE-2026-55782 · Severity: info · CVSS 2.4 · Published 2026-07-10

NanaZip is an open-source file archiver for Windows. A vulnerability in its WebAssembly file handler allows a specially crafted, small file to trigger massive memory allocations when the file is opened or extracted. This can lead to the application crashing or the system running out of memory, potentially causing a denial of service for the user.

Technologies: [M2Team NanaZip](https://junglewise.ai/threats/technologies/nanazip). Vendors: [M2Team](https://junglewise.ai/threats/vendors/m2team).

## Quick answers

**Is CVE-2026-55782 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55782 being exploited in the wild.

**How severe is CVE-2026-55782?** Informational severity, with a CVSS score of 2.4, published 10 July 2026.

**Which products and versions are affected?** M2Team NanaZip < 6.5.1749.0.

**Is there a fix for CVE-2026-55782?** A patch was published on 2026-06-16: Fixed in version 6.5.1749.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55782 attacked?** It is attacked with local access, in a network appliance.

**Am I affected by CVE-2026-55782?** Check whether you run M2Team NanaZip at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in NanaZip's WebAssembly archive handler (NanaZip.Codecs.Archive.WebAssembly.cpp) due to improper validation of ULEB128 length fields. Specifically, the 'NameSize' and 'Information.Size' fields are used to allocate std::string and std::vector buffers without being checked against the actual file size or remaining stream bytes. An attacker can provide a tiny .wasm file with a declared name length of 0xFFFFFFFF, forcing a ~4 GiB allocation during the archive listing (Open) or extraction phase. This results in a denial of service via memory exhaustion (std::bad_alloc). The issue is fixed in version 6.5.1749.0 by implementing bounds checking against the remaining bundle size.

## Affected products

- M2Team NanaZip < 6.5.1749.0

## Timeline

- 2026-06-16: advisory: GitHub Security Advisory published
- 2026-06-16: patched: Fixed in version 6.5.1749.0
- 2026-07-10: disclosed: NVD publication date

## References

- [https://github.com/M2Team/NanaZip/commit/1ce90f2d14a984476d0407a835273705607facf2](https://github.com/M2Team/NanaZip/commit/1ce90f2d14a984476d0407a835273705607facf2)
- [https://github.com/M2Team/NanaZip/commit/56aee89037947410dd5e66f3a087e0f290484bae](https://github.com/M2Team/NanaZip/commit/56aee89037947410dd5e66f3a087e0f290484bae)
- [https://github.com/M2Team/NanaZip/commit/92b12a6e1eb0cf8e88fcc277aa7508ca1ff27db6](https://github.com/M2Team/NanaZip/commit/92b12a6e1eb0cf8e88fcc277aa7508ca1ff27db6)
- [https://github.com/M2Team/NanaZip/releases/tag/6.5.1749.0](https://github.com/M2Team/NanaZip/releases/tag/6.5.1749.0)
- [https://github.com/M2Team/NanaZip/security/advisories/GHSA-qxhc-2v6p-wm8m](https://github.com/M2Team/NanaZip/security/advisories/GHSA-qxhc-2v6p-wm8m)

## Related threats

- [NanaZip SquashfsHandler heap out-of-bounds read and information disclosure](https://junglewise.ai/threats/cve-2026-54616-nanazip-squashfshandler-heap-out-of-bounds-read-and-information)
- [M2Team NanaZip NULL pointer dereference in NanaZip.Codecs archive handlers](https://junglewise.ai/threats/cve-2026-55783-m2team-nanazip-null-pointer-dereference-in-nanazip-codecs-archive)
- [M2Team NanaZip memory exhaustion in UFS and FFS image handler](https://junglewise.ai/threats/cve-2026-55781-m2team-nanazip-memory-exhaustion-in-ufs-and-ffs-image-handler)
- [M2Team NanaZip uncaught exception in .NET single-file handler](https://junglewise.ai/threats/cve-2026-55780-m2team-nanazip-uncaught-exception-in-net-single-file-handler)
- [M2Team NanaZip heap out-of-bounds read in AVB vbmeta parser](https://junglewise.ai/threats/cve-2026-47223-m2team-nanazip-heap-out-of-bounds-read-in-avb-vbmeta-parser)