The Instance::HandleInputEvent function in pdf/instance.cc in the PDFium component in Google Chrome before 38.0.2125.101 interprets a certain -1 value as an index instead of a no-visible-page error code, which allows remote attackers to cause a denial of service (out-of-bounds read) via unspecified vectors.
https://codereview.chromium.org/560133004
http://www.securityfocus.com/bid/70273
http://rhn.redhat.com/errata/RHSA-2014-1626.html
http://googlechromereleases.blogspot.com/2014/10/stable-channel-update.html