An exploitable heap-based buffer overflow exists in the Hangul Word Processor component (version 9.6.1.4350) of Hancom Thinkfree Office NEO 9.6.1.4902. A specially crafted document stream can cause an integer underflow resulting in a buffer overflow which can lead to code execution under the context of the application. An attacker can entice a user to open up a document in order to trigger this vulnerability.