The glibc packages provide the standard C libraries (libc), POSIX thread libraries (libpthread), standard math libraries (libm), and the Name Server Caching Daemon (nscd) used by multiple programs on the system. Without these libraries, the Linux system cannot function correctly. It was found that the wordexp() function would perform command substitution even when the WRDE_NOCMD flag was specified. An attacker able to provide specially crafted input to an application using the wordexp() function, and not sanitizing the input correctly, could potentially use this flaw to execute arbitrary commands with the credentials of the user running that application. (CVE-2014-7817) This issue was discovered by Tim Waugh of the Red Hat Developer Experience Team. This update also fixes the following bug: * Prior to this update, if a file stream that was opened in append mode and its underlying file descriptor were used at the same time and the file was truncated using the ftruncate() function on the file descriptor, a subsequent ftell() call on the stream incorrectly modified the file offset by seeking to the new end of the file. This update ensures that ftell() modifies the state of the file stream only when it is in append mode and its buffer is not empty. As a result, the described incorrect changes to the file offset no longer occur. (BZ#1170187) All glibc users are advised to upgrade to these updated packages, which contain backported patches to correct these issues.