Algorithmic complexity vulnerability in Email::Address::List before 0.02, as used in RT 4.2.0 through 4.2.2, allows remote attackers to cause a denial of service (CPU consumption) via a string without an address.
https://metacpan.org/changes/release/ALEXMV/Email-Address-List-0.02
http://lists.bestpractical.com/pipermail/rt-announce/2014-June/000257.html
http://blog.bestpractical.com/2014/01/security-vulnerability-in-rt-42.html