The PDF functionality in Google Chrome before 21.0.1180.57 on Mac OS X and Linux, and before 21.0.1180.60 on Windows and Chrome Frame, allows remote attackers to cause a denial of service or possibly have unspecified other impact via vectors that trigger out-of-bounds write operations.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A15053
http://googlechromereleases.blogspot.com/2012/07/stable-channel-release.html