diff --git a/src/ttyname.c b/src/ttyname.c

index ff2cacc..013be95 100644

--- a/src/ttyname.c

+++ b/src/ttyname.c

@@ -477,26 +477,38 @@ done:

 char *

 get_process_ttyname(char *name, size_t namelen)

 {

-    char path[PATH_MAX], *line = NULL;

+    const char path[] = "/proc/self/stat";

+    char *cp, buf[1024];

     char *ret = NULL;

-    size_t linesize = 0;

     int serrno = errno;

-    ssize_t len;

-    FILE *fp;

+    ssize_t nread;

+    int fd;

     debug_decl(get_process_ttyname, SUDO_DEBUG_UTIL)

-    /* Try to determine the tty from tty_nr in /proc/pid/stat. */

-    snprintf(path, sizeof(path), "/proc/%u/stat", (unsigned int)getpid());

-    if ((fp = fopen(path, "r")) != NULL) {

-	len = getline(&line, &linesize, fp);

-	fclose(fp);

-	if (len != -1) {

+    /*

+     * Try to determine the tty from tty_nr in /proc/self/stat.

+     * Ignore /proc/self/stat if it contains embedded NUL bytes.

+     */

+    if ((fd = open(path, O_RDONLY | O_NOFOLLOW)) != -1) {

+	cp = buf;

+	while ((nread = read(fd, cp, buf + sizeof(buf) - cp)) != 0) {

+	    if (nread == -1) {

+		if (errno == EAGAIN || errno == EINTR)

+		    continue;

+		break;

+	    }

+	    cp += nread;

+	    if (cp >= buf + sizeof(buf))

+		break;

+	}

+	if (nread == 0 && memchr(buf, '\0', cp - buf) == NULL) {

 	    /*

 	     * Field 7 is the tty dev (0 if no tty).

-	     * Since the process name at field 2 "(comm)" may include spaces,

-	     * start at the last ')' found.

+	     * Since the process name at field 2 "(comm)" may include

+	     * whitespace (including newlines), start at the last ')' found.

 	     */

-	    char *cp = strrchr(line, ')');

+	    *cp = '\0';

+	    cp = strrchr(buf, ')');

 	    if (cp != NULL) {

 		char *ep = cp;

 		const char *errstr;

@@ -527,7 +539,8 @@ get_process_ttyname(char *name, size_t namelen)

     errno = ENOENT;

 done:

-    free(line);

+    if (fd != -1)

+	close(fd);

     if (ret == NULL)

 	sudo_debug_printf(SUDO_DEBUG_WARN|SUDO_DEBUG_LINENO|SUDO_DEBUG_ERRNO,

 	    "unable to resolve tty via %s", path);