libpng before 1.2.37 does not properly parse 1-bit interlaced images with width values that are not divisible by 8, which causes libpng to include uninitialized bits in certain rows of a PNG file and might allow remote attackers to read portions of sensitive memory via "out-of-bounds pixels" in the file.

More... (http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2009-2042)