The base64DecodeInternal function in wtf/text/Base64.cpp in Blink, as used in Google Chrome before 34.0.1847.116, does not properly handle string data composed exclusively of whitespace characters, which allows remote attackers to cause a denial of service (out-of-bounds read) via a window.atob method call.
https://src.chromium.org/viewvc/blink?revision=170264&view=revision
https://code.google.com/p/chromium/issues/detail?id=357332
http://www.debian.org/security/2014/dsa-2905
http://security.gentoo.org/glsa/glsa-201408-16.xml
http://lists.opensuse.org/opensuse-updates/2014-05/msg00012.html
http://googlechromereleases.blogspot.com/2014/04/stable-channel-update.html