The MultipartRelatedDecoder handles the MIME boundaries incorrecly:

try

{ // [JBWS-1393] - Problem interpreting messages with attachment when confronted with no <start> header if (start == null) boundary = ("--" + boundaryParameter).getBytes("US-ASCII"); else boundary = ("\r\n--" + boundaryParameter).getBytes("US-ASCII"); }

catch (UnsupportedEncodingException e)

{ throw new WSException("US-ASCII not supported, this should never happen"); }

< EATS THE FIRST VALID MIME PART! >
// Eat first inner stream since its empty
byte[] buffer = new byte[256];
while (delimitedStream.read(buffer) != -1)
{
}

This code assumes that every MIME boundary starts with \r\n but it is not always true for the first one in the message according to RFC1521

boundary := 0*69<bchars> bcharsnospace

bchars := bcharsnospace / " "

bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" / "+" /"_"
/ "," / "-" / "." / "/" / ":" / "=" / "?"

Overall, the body of a multipart entity may be specified as
follows:

multipart-body := preamble 1*encapsulation
close-delimiter epilogue

encapsulation := delimiter body-part CRLF

delimiter := "--" boundary CRLF ; taken from Content-Type field.
; There must be no space
; between "--" and boundary.

close-delimiter := "-" boundary "-" CRLF ; Again, no space
by "--",

preamble := discard-text ; to be ignored upon receipt.

epilogue := discard-text ; to be ignored upon receipt.

discard-text := *(*text CRLF)

body-part := <"message" as defined in RFC 822,
with all header fields optional, and with the
specified delimiter not occurring anywhere in
the message body, either on a line by itself
or as a substring anywhere. Note that the
semantics of a part differ from the semantics
of a message, as described in the text.>

The problem is mayor since e.g. Axis2 generated stubs do not use \r\n before the first MIME boundary, so the MultipartRelatedDecoder eats the first MIME part which would contain the root part so after drops an exception with message "no root part was found" when MTOM is enabled at Axis2 side

Reproduction: Use any HTTP client do reproduce it.