Mozilla: Out-of-bounds read during glyph processing (MFSA 2017-11, MFSA 2017-12)

An out-of-bounds read during the processing of glyph widths during text layout. This results in a potentially exploitable crash and could allow an attacker to read otherwise inaccessible memory. This vulnerability affects Thunderbird 52.1, Firefox ESR 45.9, Firefox ESR 52.1, and Firefox 53...