The Load_SBit_Png function in sfnt/pngshim.c in FreeType before 2.5.4 does not restrict the rows and pitch values of PNG data, which allows remote attackers to cause a denial of service (integer overflow and heap-based buffer overflow) or possibly have unspecified other impact by embedding a PNG file in a .ttf font file.
Improper Restriction of Operations within the Bounds of a Memory Buffer The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary.