The xsltAddTextString function in transform.c in libxslt 1.1.29, as used in Blink in Google Chrome prior to 57.0.2987.98 for Mac, Windows, and Linux and 57.0.2987.108 for Android, lacked a check for integer overflow during a size calculation, which allowed a remote attacker to perform an out of bounds memory write via a crafted HTML page.