An Apache CXF endpoint can be used as an intermediary, where a token credential
from the received message is used as a delegation token to obtain a new token
from a Security Token Service (STS) for the outbound request.

By default, the token retrieved from the STS is cached and associated with the
delegation token via an identifier extracted from the delegation token. 

However, there is a weakness in how the identifier is extracted from the
delegation token, which means that an attacker could craft a token which 
would return an identifer corresponding to a cached token for another user.

External References:

http://cxf.apache.org/security-advisories.data/CVE-2017-5656.txt.asc

Upstream patch:

https://github.com/apache/cxf/commit/66c2c5b99e01a2165a2c5ed9ae34b4b9a512cb39