CVE 2015-8540
Integer underflow in the png_check_keyword function in pngwutil.c in libpng 0.90 through 0.99, 1.0.x before 1.0.66, 1.1.x and 1.2.x before 1.2.56, 1.3.x and 1.4.x before 1.4.19, and 1.5.x before 1.5.26 allows remote attackers to have unspecified impact via a space character as a keyword in a PNG image, which triggers an out-of-bounds read.
See the 
CVE page on Mitre.org
for more details.
