Release notes for Exim 4.76 says:
Bugzilla 1106: CVE-2011-1764 - DKIM log line was subject to a format-string attack -- SECURITY: remote arbitrary code execution. DKIM signature header parsing was double-expanded, second time unintentionally subject to list matching rules, letting the header cause arbitrary Exim lookups (of items which can occur in lists, not arbitrary string expansion). This allowed for information disclosure.
Also, impact assessment was redone shortly after the original announcement:
Further analysis revealed that the second security was more severe than I realised at the time that I wrote the announcement. The second security issue has been assigned CVE-2011-1407 and is also a remote code execution flaw. For clarity: both issues were introduced with 4.70.