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MessagePackSerializer.Deserialize<dynamic> hangs permanently #359

Metalnem opened this Issue Dec 28, 2018 · 2 comments


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Metalnem commented Dec 28, 2018

The following C# program hangs permanently:

namespace MessagePack.Run
  public class Program
    public static void Main(string[] args)
      var bytes = new byte[]
        0x8E, 0x80, 0xFF, 0x74, 0x6F, 0x0E, 0x41, 0xDF, 0x74,
        0x6F, 0x0E, 0x41, 0x90, 0x00, 0x00, 0x0F, 0x7B, 0x20,
        0x8E, 0x80, 0xFF, 0x74, 0x6F, 0x0E, 0x41, 0xDF, 0x74,
        0x6F, 0x0E, 0x41, 0x90, 0x00, 0x00, 0xF8, 0x7A, 0x20,
        0x70, 0x68, 0x00, 0xDF, 0x6F, 0x90, 0x1C, 0x6F, 0x74,
        0x6F, 0x61, 0x70, 0x68, 0x00, 0xDF, 0x52, 0x90, 0x1C,
        0x6F, 0x74, 0x6F, 0x61, 0x6D, 0x01, 0x02, 0x03, 0x04


Found via SharpFuzz.


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itn3000 commented Jan 7, 2019

In my env, OutOfMemoryException occurred(win81-x64).
MessagePack.dll seems to interprete the data as follows(msgpack spec is here);

  1. 0x8e = fixmap, length = 14(let's say "mapA")
  2. 0x80 = fixmap, length = 0(1st mapA key)
  3. 0xff = negative fixint = -1(1st mapA value)
  4. 0x74 = positive fixint = 0x74(2nd mapA key)
  5. 0x6f = positive fixint = 0x6f(2nd mapA value)
  6. 0x0e = positive fixint = 0x0e(3rd mapA key)
  7. 0x41 = positive fixint = 0x41(3rd mapA value)
  8. 0xdf = map32(4th mapA key)
  9. 0x74, 0x6f, 0x0e, 0x41 = map32 length(0x746f0e41 = 1953435201)
  10. do new Dictionary<object, object>(1953435201)

this is very large object, so program may be freeze or throw OutOfMemoryException(depending on the environment)

I think the decoder should throw any Exception in processing(perhaps IndexOutOfRangeException?) if map or array length is exceeded remaining data length.


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Metalnem commented Jan 9, 2019

This is interesting. I've tried it on .NET Framework 4.7.2, and I also got OutOfMemoryException, but on .NET Core 2.1 this program hangs on both Windows and macOS. This looks like it could actually be some .NET Core bug. I'll investigate this a bit further!

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