The TIFFFetchNormalTag function in LibTiff 4.0.6 allows remote attackers to cause a denial of service (out-of-bounds read) via crafted TIFF_SETGET_C16ASCII or TIFF_SETGET_C32_ASCII tag values.
https://security.gentoo.org/glsa/201701-16
http://www.debian.org/security/2017/dsa-3762