In Apache SpamAssassin before 3.4.3, a message can be crafted in a way to use excessive resources. Upgrading to SA 3.4.3 as soon as possible is the recommended fix but details will not be shared publicly.
{ "urgency": "not yet assigned" }
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2019-12420.json"