diff --git a/modules/pam_timestamp/pam_timestamp.c b/modules/pam_timestamp/pam_timestamp.c
index 5193733..b3f08b1 100644
--- a/modules/pam_timestamp/pam_timestamp.c
+++ b/modules/pam_timestamp/pam_timestamp.c
@@ -158,7 +158,7 @@ check_tty(const char *tty)
 		tty = strrchr(tty, '/') + 1;
 	}
 	/* Make sure the tty wasn't actually a directory (no basename). */
-	if (strlen(tty) == 0) {
+	if (!strlen(tty) || !strcmp(tty, ".") || !strcmp(tty, "..")) {
 		return NULL;
 	}
 	return tty;
@@ -243,6 +243,17 @@ get_ruser(pam_handle_t *pamh, char *ruserbuf, size_t ruserbuflen)
 		if (pwd != NULL) {
 			ruser = pwd->pw_name;
 		}
+	} else {
+		/*
+		 * This ruser is used by format_timestamp_name as a component
+		 * of constructed timestamp pathname, so ".", "..", and '/'
+		 * are disallowed to avoid potential path traversal issues.
+		 */
+		if (!strcmp(ruser, ".") ||
+		    !strcmp(ruser, "..") ||
+		    strchr(ruser, '/')) {
+			ruser = NULL;
+		}
 	}
 	if (ruser == NULL || strlen(ruser) >= ruserbuflen) {
 		*ruserbuf = '\0';