CVE 2008-4813
Adobe Reader and Acrobat 8.1.2 and earlier, and before 7.1.1, allow remote attackers to execute arbitrary code via a crafted PDF document that (1) performs unspecified actions on a Collab object that trigger memory corruption, related to a GetCosObj method; or (2) contains a malformed PDF object that triggers memory corruption during parsing.
See the 
CVE page on Mitre.org
for more details.
