This vulnerability affects Exim instances built with DKIM
enabled (this is the default for FreeBSD Exim port) and running
verification of DKIM signatures on the incoming mail
messages.
This is a SECURITY release, addressing a CRITICAL remote
code execution flaw in versions of Exim between 4.70 and
4.80 inclusive, when built with DKIM support (the default).
This security vulnerability can be exploited by anyone
who can send email from a domain for which they control the
DNS.
You are not vulnerable if you built Exim with DISABLE_DKIM
or if you put this at the start of an ACL plumbed into
acl_smtp_connect or acl_smtp_rcpt:
warn control = dkim_disable_verify