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

Summary MessagePack-CSharp's typeless deserialization includes MessagePackSerializerOptions.ThrowIfDeserializingTypeIsDisallowedType 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 typ...

GHSA-QHMF-XW27-6RQR MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments

Summary MessagePack-CSharp's typeless deserialization includes MessagePackSerializerOptions.ThrowIfDeserializingTypeIsDisallowedType 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 typ...

Inefficient Algorithmic Complexity

Overview MessagePack is a MessagePackMsgPack Serializer for C.NET, .NET Core, Unity, Xamarin. Affected versions of this package are vulnerable to Inefficient Algorithmic Complexity in the InterfaceLookupFormatter process. An attacker can cause excessive CPU consumption by supplying specially...

EUVD-2026-38380

MessagePack-CSharp: InterfaceLookupFormatter bypasses collision-resistant comparer settings...

MessagePack-CSharp: InterfaceLookupFormatter bypasses collision-resistant comparer settings

Summary InterfaceLookupFormatter constructs an internal Dictionary with the default equality comparer instead of the security-aware comparer supplied by options.Security.GetEqualityComparer. Other hash-based collection formatters use the security-aware comparer when...

Allocation of Resources Without Limits or Throttling

Overview MessagePack is a MessagePackMsgPack Serializer for C.NET, .NET Core, Unity, Xamarin. Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling in the deserialization process for multi-dimensional arrays. An attacker can cause excessive memor...

EUVD-2026-38381

MessagePack-CSharp: Multi-dimensional array formatters allocate from unchecked dimensions...

GHSA-W567-GJR2-HM5J MessagePack-CSharp: Unity unsafe blit formatter allocates from unbounded byte length

Summary UnsafeBlitFormatterBase.Deserialize reads an attacker-controlled byteLength from an extension payload and allocates an array based on that value before validating it against the extension header length or remaining payload bytes. The outer extension header is bounded by available input, b...

GHSA-WFR3-XJ75-PFWH MessagePack-CSharp: DynamicUnionResolver-generated deserializers miss depth enforcement

Summary Runtime-generated union deserializers emitted by DynamicUnionResolver do not call MessagePackSecurity.DepthStepref reader and do not decrement reader.Depth around recursive deserialization and skip paths. This means union deserialization does not consistently participate in the maximum...

MessagePack-CSharp: DynamicUnionResolver-generated deserializers miss depth enforcement

Summary Runtime-generated union deserializers emitted by DynamicUnionResolver do not call MessagePackSecurity.DepthStepref reader and do not decrement reader.Depth around recursive deserialization and skip paths. This means union deserialization does not consistently participate in the maximum...

Uncontrolled Recursion

Overview MessagePack is a MessagePackMsgPack Serializer for C.NET, .NET Core, Unity, Xamarin. Affected versions of this package are vulnerable to Uncontrolled Recursion in the DynamicUnionResolver.BuildDeserialize process. An attacker can cause a process crash by providing a specially crafted uni...

GHSA-CJ9G-3MJ2-G8VV MessagePack-CSharp: JSON conversion APIs can recurse without consistent depth enforcement

Summary MessagePack-CSharp's JSON conversion helpers contain multiple recursion paths that do not consistently enforce a depth limit. These paths are in the JSON conversion component rather than normal typed MessagePack deserialization. Three related issues are covered by this advisory: 1...

MessagePack-CSharp: JSON conversion APIs can recurse without consistent depth enforcement

Summary MessagePack-CSharp's JSON conversion helpers contain multiple recursion paths that do not consistently enforce a depth limit. These paths are in the JSON conversion component rather than normal typed MessagePack deserialization. Three related issues are covered by this advisory: 1...

Uncontrolled Recursion

Overview MessagePack is a MessagePackMsgPack Serializer for C.NET, .NET Core, Unity, Xamarin. Affected versions of this package are vulnerable to Uncontrolled Recursion in the JSON conversion process. An attacker can cause the application to exhaust the process stack and terminate unexpectedly by...

Inefficient Algorithmic Complexity

Overview MessagePack is a MessagePackMsgPack Serializer for C.NET, .NET Core, Unity, Xamarin. Affected versions of this package are vulnerable to Inefficient Algorithmic Complexity through the ExpandoObjectFormatter.Deserialize process. An attacker can cause excessive CPU consumption and memory...

EUVD-2026-38385

MessagePack-CSharp: ExpandoObject formatter can perform quadratic insertion work on untrusted maps...

MessagePack-CSharp: ExpandoObject formatter can perform quadratic insertion work on untrusted maps

Summary ExpandoObjectFormatter.Deserialize populates System.Dynamic.ExpandoObject by calling IDictionary.Add for each map entry. ExpandoObject internally maintains member names in array-like structures, so inserting many distinct keys can require repeated linear scans and array copies. For large...

GHSA-2X83-8G95-XH59 MessagePack-CSharp: ExpandoObject formatter can perform quadratic insertion work on untrusted maps

Summary ExpandoObjectFormatter.Deserialize populates System.Dynamic.ExpandoObject by calling IDictionary.Add for each map entry. ExpandoObject internally maintains member names in array-like structures, so inserting many distinct keys can require repeated linear scans and array copies. For large...

MessagePack-CSharp: LZ4 decompression allocates from unbounded declared output lengths

Summary When MessagePack-CSharp decompresses Lz4Block or Lz4BlockArray payloads, it reads declared uncompressed lengths from the wire and allocates output buffers based on those lengths before validating that the compressed data is valid or that the declared expansion is reasonable. A small paylo...

Allocation of Resources Without Limits or Throttling

Overview MessagePack is a MessagePackMsgPack Serializer for C.NET, .NET Core, Unity, Xamarin. Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling via the TryDecompress process. An attacker can cause excessive memory allocation and potential...