The libtiff packages contain a library of functions for manipulating Tagged Image File Format files. A heap-based buffer overflow flaw was found in the way libtiff processed certain TIFF files encoded with a 4-bit run-length encoding scheme from ThunderScan. An attacker could use this flaw to create a specially-crafted TIFF file that, when opened, would cause an application linked against libtiff to crash or, possibly, execute arbitrary code. This update also fixes the following bug: * The RHSA-2011:0318 libtiff update introduced a regression that prevented certain TIFF Internet Fax image files, compressed with the CCITT Group 4 compression algorithm, from being read. All libtiff users should upgrade to these updated packages, which contain a backported patch to resolve these issues. All running applications linked against libtiff must be restarted for this update to take effect.