1 files changed, 5 insertions, 1 deletions
diff --git a/apps/s_client.c b/apps/s_client.c
index 3625f8fcdc99..d356359a97ef 100644
--- a/apps/s_client.c
+++ b/apps/s_client.c
@@ -3892,7 +3892,11 @@ static void user_data_init(struct user_data_st *user_data, SSL *con, char *buf,
 
 static int user_data_add(struct user_data_st *user_data, size_t i)
 {
-    if (user_data->buflen != 0 || i > user_data->bufmax)
+    /*
+     * We must allow one byte for a NUL terminator so i must be less than
+     * bufmax
+     */
+    if (user_data->buflen != 0 || i >= user_data->bufmax)
         return 0;
 
     user_data->buflen = i;