The MITRE CVE dictionary describes this issue as:
The LZW decompressor in the LWZReadByte function in giftoppm.c in the David Koblas GIF decoder in PBMPLUS, as used in the gif_read_lzw function in filter/image-gif.c in CUPS before 1.4.7, the LZWReadByte function in plug-ins/common/file-gif-load.c in GIMP 2.6.11 and earlier, the LZWReadByte function in img/gifread.c in XPCE in SWI-Prolog 5.10.4 and earlier, and other products, does not properly handle code words that are absent from the decompression table when encountered, which allows remote attackers to trigger an infinite loop or a heap-based buffer overflow, and possibly execute arbitrary code, via a crafted compressed stream, a related issue to CVE-2006-1168 and CVE-2011-2895.
Find out more about CVE-2011-2896 from the
MITRE CVE dictionary dictionary and
Vulnerable. This issue affects the versions of cups as shipped with Red Hat Enterprise Linux 4, 5, and 6. The Red Hat Security Response Team has rated this issue as having moderate security impact for the cups package. A future update may address this issue in the cups package for Red Hat Enterprise Linux 4, 5, and 6. For additional information, refer to the Issue Severity Classification: