It SOUNDs like one of two things:
1) You have MTOM enabled. Usually this is via config somehow, but can also be enabled via an @MTOM annotation.
2) The WSDL that is used contains a MIME binding and thus Soap w/ attachments is turned on.
Normally, CXF doesn't put the response into MIME form unless one of the above is true.
Thanks a lot, mtom was enabled on the jaxws endpoint. I disabled it and now it is as expected:
<soap:soapBinding mtomEnabled="false" version="1.2"/>