# CVE-2020-5234: Untrusted data can lead to DoS attack due to hash collisions and stack overflow in MessagePack

Source: https://junglewise.ai/threats/cve-2020-5234-untrusted-data-can-lead-to-dos-attack-due-to-hash-collisions-and  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2020-01-31  
License: CC BY 4.0 with a link back

CVE-2020-5234 · Severity: low · CVSS 3.1 · Published 2020-01-31

Untrusted data can lead to DoS attack due to hash collisions and stack overflow in MessagePack

Technologies: [MessagePack (NuGet)](https://junglewise.ai/threats/technologies/messagepack). Vendors: [NuGet](https://junglewise.ai/threats/vendors/nuget).

## Quick answers

**Is CVE-2020-5234 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2020-5234 being exploited in the wild.

**How severe is CVE-2020-5234?** Low severity, with a CVSS score of 3.1, published 31 January 2020.

**Which products and versions are affected?** MessagePack (NuGet) ECOSYSTEM:introduced=0,fixed=1.9.11; MessagePack.ImmutableCollection (NuGet) ECOSYSTEM:introduced=0,fixed=1.9.11; MessagePack.ReactiveProperty (NuGet) ECOSYSTEM:introduced=0,fixed=1.9.11; MessagePack.Unity (NuGet) ECOSYSTEM:introduced=0,fixed=1.9.11; and 1 more.

**Is there a fix for CVE-2020-5234?** Yes. MessagePack (NuGet): upgrade to 1.9.11 or later; MessagePack.ImmutableCollection (NuGet): upgrade to 1.9.11 or later; MessagePack.ReactiveProperty (NuGet): upgrade to 1.9.11 or later; MessagePack.Unity (NuGet): upgrade to 1.9.11 or later; MessagePack.UnityShims (NuGet): upgrade to 1.9.11 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2020-5234?** Check whether you run MessagePack (NuGet), MessagePack.ImmutableCollection (NuGet), MessagePack.ReactiveProperty (NuGet) or one of the others listed 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.

## How to fix

- MessagePack (NuGet): upgrade to 1.9.11 or later

  ```sh
  dotnet add package MessagePack --version 1.9.11
  ```

- MessagePack.ImmutableCollection (NuGet): upgrade to 1.9.11 or later

  ```sh
  dotnet add package MessagePack.ImmutableCollection --version 1.9.11
  ```

- MessagePack.ReactiveProperty (NuGet): upgrade to 1.9.11 or later

  ```sh
  dotnet add package MessagePack.ReactiveProperty --version 1.9.11
  ```

- MessagePack.Unity (NuGet): upgrade to 1.9.11 or later

  ```sh
  dotnet add package MessagePack.Unity --version 1.9.11
  ```

- MessagePack.UnityShims (NuGet): upgrade to 1.9.11 or later

  ```sh
  dotnet add package MessagePack.UnityShims --version 1.9.11
  ```


## Affected products

- MessagePack (NuGet) ECOSYSTEM:introduced=0,fixed=1.9.11
- MessagePack.ImmutableCollection (NuGet) ECOSYSTEM:introduced=0,fixed=1.9.11
- MessagePack.ReactiveProperty (NuGet) ECOSYSTEM:introduced=0,fixed=1.9.11
- MessagePack.Unity (NuGet) ECOSYSTEM:introduced=0,fixed=1.9.11
- MessagePack.UnityShims (NuGet) ECOSYSTEM:introduced=0,fixed=1.9.11

## Identifiers

- CVE-2020-5234
- GHSA-7q36-4xx7-xcxf

## Related threats

- [MessagePack-CSharp memory exhaustion in nested array deserialization](https://junglewise.ai/threats/cve-2026-92707-messagepack-nested-arrays-can-blow-past-buffer-length-limits)
- [MessagePack for C# security bypass in typeless deserialization](https://junglewise.ai/threats/cve-2026-48517-messagepack-for-c-security-bypass-in-typeless-deserialization)
- [MessagePack for C# hash-collision DoS in InterfaceLookupFormatter](https://junglewise.ai/threats/cve-2026-48516-messagepack-for-c-hash-collision-dos-in-interfacelookupformatter)
- [MessagePack for C# resource exhaustion in multi-dimensional array formatters](https://junglewise.ai/threats/cve-2026-48515-messagepack-for-c-resource-exhaustion-in-multi-dimensional-array)
- [MessagePack for C# denial of service in UnsafeBlitFormatterBase](https://junglewise.ai/threats/cve-2026-48514-messagepack-for-c-denial-of-service-in-unsafeblitformatterbase)