A security vulnerability has been identified and fixed in pidgin:

It has been discovered that eight denial of service conditions exist
in libpurple all due to insufficient validation of the return value
from purple_base64_decode(). Invalid or malformed data received in
place of a valid base64-encoded value in portions of the Yahoo!, MSN,
MySpaceIM, and XMPP protocol plugins and the NTLM authentication
support trigger a crash. These vulnerabilities can be leveraged by
a remote user for denial of service (CVE-2010-3711).

Packages for 2009.0 are provided as of the Extended Maintenance
Program. Please visit this link to learn more:
http://store.mandriva.com/product_info.php?cPath=149&products_id=490

This update provides pidgin 2.7.4, which is not vulnerable to this
issue.