An overflow exists in the Pegasus mail client. The MUA fails to process long headers over 259 characters in the To: or From: fields resulting in a buffer overflow. With a specially crafted request, an attacker can cause a crash or possibly execute code resulting in a loss of integrity and/or availability.
Loss of Availability
Upgrade to version Pegasus Mail 4.02 or higher, as it has been reported to fix this vulnerability. An upgrade is required as there are no known workarounds.