CVE 2009-1375
The PurpleCircBuffer implementation in Pidgin (formerly Gaim) before 2.5.6 does not properly maintain a certain buffer, which allows remote attackers to cause a denial of service (memory corruption and application crash) via vectors involving the (1) XMPP or (2) Sametime protocol.
See the 
CVE page on Mitre.org
for more details.
