Asterisk Project Security Advisory – 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.