# CVE-2026-55780: NanaZip: Uncaught exception / unbounded allocation in NanaZip .NET single-file Extract() via unvalidated entry Size

> A crafted .NET single-file bundle can cause an unhandled exception and crash NanaZip due to unvalidated entry size fields.

- **Severity:** Low 2.4 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 10 Jul 2026
- **Updated:** 13 Jul 2026
- **Also known as:** GHSA-ppm9-5267-rq72

## What is CVE-2026-55780?

CVE-2026-55780 is a low-severity denial of service vulnerability in M2Team NanaZip, published on 10 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

NanaZip is the 7-Zip derivative intended for the modern Windows experience. Prior to 6.5.1749.0, NanaZip's .NET single-file bundle handler in NanaZip.Codecs.Archive.DotNetSingleFile.cpp sizes its extraction buffer from the bundle entry Size field, which is only checked for sign and is not validated against the real file size. A crafted bundle can cause an attacker-chosen allocation inside Extract, where std::bad_alloc or std::length_error can escape across the COM STDMETHODCALLTYPE boundary and crash the process. This issue is fixed in version 6.5.1749.0.

Weakness: CWE-400 (Uncontrolled Resource Consumption), CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2026-55780?


## How do I fix CVE-2026-55780?

No fix has been published for CVE-2026-55780 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-55780 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55780 exists.

Public exploit code:

- NanaZip 6.5  -  DoS (exploitdb)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55780 and fix it if it is affected.

What it is: CVE-2026-55780 is a low-severity denial of service vulnerability in M2Team NanaZip, published on 10 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55780 exists.

Affected product: M2Team NanaZip. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-55780/ (Markdown: https://insights.sbomify.com/CVE-2026-55780/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55780
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55780
- OSV: https://osv.dev/vulnerability/CVE-2026-55780

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55780/
Summaries are generated and may contain mistakes; the official description above is the record.