The XULContentSinkImpl::AddText function in Mozilla Firefox before 41.0 and Firefox ESR 38.x before 38.3 might allow remote attackers to cause a denial of service (memory corruption and application crash) or possibly have unspecified other impact via unknown vectors, related to an "overflow."
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.