OpenDMARC is an open source DMARC implementation.
It was found that OpenDMARC did not properly handle DMARC aggregate reports.
A remote attacker, by sending a specially crafted DMARC aggregate report, could possibly cause a Denial of Service condition and depending on how OpenDMARC library is used in linked application execute arbitrary code with the privileges of the process.
There is no known workaround at this time.
All OpenDMARC users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=mail-filter/opendmarc-1.3.3"