Description

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePack-CSharp's typeless deserialization includes MessagePackSerializerOptions.ThrowIfDeserializingTypeIsDisallowed(Type) as a safety check for dangerous types. The default implementation checks the outer type name, but it does not recursively inspect array element types or generic type arguments. As a result, a type that would be blocked directly can be wrapped inside an array or constructed generic type and pass the outer type check. The formatter machinery can then materialize formatters for the inner blocked type. This vulnerability is fixed in 2.5.301 and 3.1.7.

Severity (CVSS)

Base score6.3
SeverityMedium
VersionCVSS 4.0
VectorCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Provided byCNA

Weaknesses

  • CWE-470 — CWE-470: Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')
  • CWE-502 — CWE-502: Deserialization of Untrusted Data

Affected products

VendorProductVersions
MessagePack-CSharpMessagePack-CSharp>= 3.1.7, < 3.1.7; < 2.5.301

References

Authoritative sources

This page is a snapshot. For the latest enrichment and updates, view the record on CVE.org or the NVD.

Generated from the official CVE List on 23 Jun 2026 10:05 UTC.