Core Security Technologies reported that previous upstream fixes addressing insufficient input validation flaw in pidgin / libpurple in function msnslplinkprocessmsg() are inefficient and can be bypassed. This flaw allows an attacker to overwrite pidgin's memory and possibly execute arbitrary code with the privileges of the user running application using libpurple.
This issue was previously tracked as CVE-2008-2927 (bug #453764) and CVE-2009-1376 (bug #500493, incomplete fix).
The OSCAR protocol plugin in libpurple in Pidgin before 2.6.3 and Adium before 1.3.7 allows remote attackers to cause a denial of service (application crash) via crafted contact-list data for (1) ICQ and possibly (2) AIM, as demonstrated by the SIM IM client.