fedora 25
format weakness #13


Weakness Breakdown


A format string exploit occurs when the data of an input string is evaluated as a command by the program. This class of attacks is very similar to buffer overflows since an attacker could execute code, read the stack or cause new behaviors that compromise security. Learn more about format string attacks on OWASP attack index.

Warning code(s):

If format strings can be influenced by an attacker, they can be exploited, and note that sprintf variations do not always 0-terminate.

File Name:



The highlighted line of code below is the trigger point of this particular Fedora 25 format weakness.

 #ifndef lint
static char sccsid[] = "@(#)uucplock.c	5.5 (Berkeley) 6/1/90";
#endif /* not lint */

#include <sys/file.h>
#include <sys/dir.h>
#include <errno.h>

#include "pathnames.h"

 * uucp style locking routines
 * return: 0 - success
 * 	  -1 - failure

	char *ttyname;
	extern int errno;
	int fd, pid;
	char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN];
	off_t lseek();

	(void)snprintf(tbuf, sizeof(tbuf), _PATH_LOCKDIRNAME, ttyname);
	fd = open(tbuf, O_RDWR|O_CREAT|O_EXCL, 0664);
	if (fd < 0) {
		 * file is already locked
		 * check to see if the process holding the lock still exists
		fd = open(tbuf, O_RDWR, 0);
		if (fd < 0) {
			perror("lock open");
		if (read(fd, &pid, sizeof(pid)) != sizeof(pid)) {
			perror("lock read");

		if (kill(pid, 0) == 0 || errno != ESRCH) {
			(void)close(fd);	/* process is still running */
		 * The process that locked the file isn't running, so
		 * we'll lock it ourselves

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