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...

CVE-2026-48511

MessagePack for C is a MessagePack serializer for C. Prior to 2.5.301 and 3.1.7, 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...