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.
https://www.redhat.com/archives/fedora-package-announce/2009-June/msg00075.html
https://www.redhat.com/archives/fedora-package-announce/2009-June/msg00051.html
https://www.redhat.com/archives/fedora-package-announce/2009-June/msg00033.html
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10829
https://exchange.xforce.ibmcloud.com/vulnerabilities/50683
https://bugzilla.redhat.com/show_bug.cgi?id=500491
http://www.vupen.com/english/advisories/2009/1396
http://www.ubuntu.com/usn/USN-781-1
http://www.securityfocus.com/bid/35067
http://www.redhat.com/support/errata/RHSA-2009-1060.html
http://www.pidgin.im/news/security/?id=31
http://www.mandriva.com/security/advisories?name=MDVSA-2009:173
http://www.gentoo.org/security/en/glsa/glsa-200905-07.xml
http://secunia.com/advisories/35329
http://secunia.com/advisories/35294
http://secunia.com/advisories/35215
http://secunia.com/advisories/35202
http://secunia.com/advisories/35194