When opening a Hangul Hcell Document (.cell) and processing a particular record within the Workbook stream, an index miscalculation leading to a heap overlow can be made to occur in Hancom Office 2014. The vulnerability occurs when processing data for a formula used to render a chart via the HncChartPlugin.hplg library. Due to a lack of bounds-checking when incrementing an index that is used for writing into a buffer for formulae, the application can be made to write pointer data outside its bounds which can lead to code execution under the context of the application.