CVE-2026-48517

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

Published Jun 22, 2026 CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-qhmf-xw27-6rqr MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments
History
Type Values Removed Values Added
First Time appeared Messagepack
Messagepack messagepack-csharp
Vendors & Products Messagepack
Messagepack messagepack-csharp
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments
Weaknesses CWE-470
CWE-502
References
Metrics cvssV4_0

{'score': 6.3, '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jun 25, 2026, 3:55 PM
Reserved
May 21, 2026, 4:18 PM
Status
Analyzed
Published
Jun 22, 2026, 10:16 PM
Modified
Jun 25, 2026, 5:16 PM