The Sendmail Consortium has released version 8.12.9 of the Sendmail Mail Transfer Agent (SMTP server) after a serious vulnerability having to do with the parsing of addresses was prematurely revealed by a third party.
As explained on the Sendmail site, the address parsing problem was a buffer overflow with potentially serious consequences. The advisory does not specifically recommend that administrators install the patches, but the use of the term critical security flaw is suggestive.