Andrey Kiselev discovered a problem in the TIFF library that may allow an attacker with a specially crafted TIFF image with Yr/Yg/Yb values that exceed the YCR/YCG/YCB values to crash the library and hence the surrounding application.
The old stable distribution (woody) is not affected by this problem.
For the stable distribution (sarge) this problem has been fixed in version 3.7.2-4.
The unstable distribution (sid) is not affected by this problem.
We recommend that you upgrade your tiff packages and restart the programs using it.