log4j:log4j is a the 1.x branch of the Apache Log4j project.
Affected versions of this package are vulnerable to Man-in-the-Middle (MitM). Improper validation of certificate with host mismatch in Apache Log4j SMTP appender. This could allow an SMTPS connection to be intercepted by a man-in-the-middle attack which could leak any log messages sent through that appender.
There is no fixed version for