Asterisk Open Source 1.4.5 through 1.4.11, when configured to use an IMAP voicemail storage backend, allows remote attackers to cause a denial of service via an e-mail with an "invalid/corrupted" MIME body, which triggers a crash when the recipient listens to voicemail.
Asterisk Project Security Advisory - Asterisk suffers from a crash vulnerability when passed invalid MIME bodies when using voicemail with IMAP storage.