The browser engine in Mozilla Firefox 3.0.x before 3.0.18, 3.5.x before 3.5.8, and 3.6.x before 3.6.2; Thunderbird before 3.0.2; and SeaMonkey before 2.0.3 allows remote attackers to cause a denial of service (memory corruption and application crash) and possibly execute arbitrary code via vectors related to (1) layout/generic/nsBlockFrame.cpp and (2) the _evaluate function in modules/plugin/base/src/nsNPAPIPlugin.cpp.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.