Compiler Engineer Dan Gohman of Google reported that binary search algorithms in the SpiderMonkey JavaScript engine were prone to overflow in several places, leading to potential out-of-bounds array access. While none of these are known to be directly exploitable, they are unsafe in theory and have been changed as part of general security improvements.
In general these flaws cannot be exploited through email in the Thunderbird and Seamonkey products because scripting is disabled, but are potentially a risk in browser or browser-like contexts.
Vulmon