MessagePack-CSharp MessagePack for C# up to 2.5.300/3.1.6 externally-controlled input to select classes or code

Summaryinfo

A vulnerability, which was classified as problematic, has been found in MessagePack-CSharp MessagePack for C# up to 2.5.300/3.1.6. This issue affects some unknown processing. Performing a manipulation results in use of externally-controlled input to select classes or code. This vulnerability is cataloged as CVE-2026-48517. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in MessagePack-CSharp MessagePack for C# up to 2.5.300/3.1.6. It has been classified as problematic. This affects an unknown functionality. The manipulation with an unknown input leads to a use of externally-controlled input to select classes or code vulnerability. CWE is classifying the issue as CWE-470. The product uses external input with reflection to select which classes or code to use, but it does not sufficiently prevent the input from selecting improper classes or code. This is going to have an impact on integrity. The summary by CVE 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 advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-48517 since 05/21/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available.

Upgrading to version 2.5.301 or 3.1.7 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• MessagePack-CSharp

Name

• MessagePack for C#

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5.300
• 3.1.0
• 3.1.1
• 3.1.2
• 3.1.3
• 3.1.4
• 3.1.5
• 3.1.6

CPE 2.3info

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CPE 2.2info

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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