CVE-2026-48517CWE-470CWE-502

MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments

Medium · published June 22, 2026

CVSS v4.0
6.3
EPSS
0%
Percentile
27.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
6.3 · MEDIUM
Vector
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
EPSS
0.00348 · 27.1th percentile
Weaknesses
CWE-470 · Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection'); CWE-502 · Deserialization of Untrusted Data
Published
2026-06-22T21:03Z
EPSS history
Timeline
  • 22 JUN 21:03Z
    MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments
    cvelistv5