rfc822.c in Mutt through 2.0.4 allows remote attackers to cause a denial of service (mailbox unavailability) by sending email messages with sequences of semicolon characters in RFC822 address fields (aka terminators of empty groups).
A small email message from the attacker can cause large memory consumption, and the victim may then be unable to see email messages from other persons.
For Debian 8 jessie, these problems have been fixed in version 1.5.23-3+deb8u5.
We recommend that you upgrade your mutt packages.
Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/