asterisk and pjsip -- multiple vulnerabilities

The Asterisk project reports:

AST-2018-002 - By crafting an SDP message with an invalid media format description Asterisk crashes when using the pjsip channel driver because pjproject's sdp parsing algorithm fails to catch the invalid media format description.

AST-2018-003 - By crafting an SDP message body with an invalid fmtp attribute Asterisk crashes when using the pjsip channel driver because pjproject's fmtp retrieval function fails to check if fmtp value is empty (set empty if previously parsed as invalid).

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