Skip to main content
← All vulnerabilities
CVE-2026-48509GHSA-2F33-PR97-265Q

MessagePack-CSharp: ASP.NET Core MessagePackInputFormatter defaults to TrustedData for HTTP request bodies

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 3.1.7, 2.5.301
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: partial

Summary

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, the parameterless MessagePackInputFormatter() constructor uses default serializer options, which resolve to MessagePackSerializerOptions.Standard with MessagePackSecurity.TrustedData. The formatter is designed for ASP.NET Core MVC request bodies, which commonly cross an HTTP trust boundary. This insecure default can expose applications to denial-of-service attacks that MessagePackSecurity.UntrustedData is intended to mitigate, such as hash-collision attacks against dictionary-like model properties. This vulnerability is fixed in 2.5.301 and 3.1.7.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: partial

  3. Record last updated

Affected versions

  • MessagePack-CSharp MessagePack-CSharp

    From 3.0 · fixed in 3.1.7; fixed in 2.5.301

  • MessagePackNuGet

    fixed in 2.5.301

  • MessagePackNuGet

    From 3.0 · fixed in 3.1.7

References 1

GitHub · MessagePack-CSharp/MessagePack-CSharp