The following security flaw has been found in the way gdk-pixbuf, an image
loading library, loaded certain Graphics Interchange Format (GIF) image files:
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It was found that gdk-pixbuf GIF image loader gdk_pixbuf__gif_image_load()
routine did not properly handle certain return values from its subroutines.
A remote attacker could provide a specially-crafted GIF image, which once
opened in an application, linked against gdk-pixbuf would lead to gdk-pixbuf
to return partially initialized pixbuf structure, possibly having huge
width and height, leading to that particular application termination due
excessive memory use.

References:

[1] https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2011-2485
[2] http://git.gnome.org/browse/gdk-pixbuf/commit/?id=f8569bb13e2aa1584dde61ca545144750f7a7c98

For Pidgin the above gdk-pixbuf library deficiency would mean:
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A remote attacker could set a specially-crafted GIF image as their buddy icon that could lead to Pidgin being terminated due to excessive memory use.

References:
[3] http://www.pidgin.im/news/security/?id=52

Acknowledgements:

Red Hat would like to thank the Pidgin project for reporting this issue.
Upstream acknowledges Mark Doliner as the original reporter.