When an out of call message - delivered by either the
SIP or PJSIP channel driver or the XMPP stack - is handled
in Asterisk, a crash can occur if the channel servicing
the message is sent into the ReceiveFax dialplan application
while using the res_fax_spandsp module.
Note that this crash does not occur when using the
res_fax_digium module. While this crash technically
occurs due to a configuration issue, as attempting to
receive a fax from a channel driver that only contains
textual information will never succeed, the likelihood
of having it occur is sufficiently high as to warrant
this advisory.