This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Mozilla Firefox. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.
The specific flaw exists within handling of references to external font resources. A value is used as a 16 bit integer in an array allocation and later as 32 bit when iterating over and then populating these fields. By creating enough references, a remote attacker can exploit this vulnerability to execute arbitrary code under the context of the browser.