Check for invalid short Alert messages

(Short Change Cipher Spec & Handshake messages are already checked for.)
diff --git a/ChangeLog b/ChangeLog
index acf4b4b..d2ce6ef 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -20,6 +20,8 @@
      seen when communicating with OpenSSL using TLS 1.0. Reported by @kFYatek
      (#1632) and by Conor Murphy on the forum. Fix contributed by Espressif
      Systems.
+   * Fail when receiving a TLS alert message with an invalid length, or invalid
+     zero-length messages when using TLS 1.2. Contributed by Espressif Systems.
 
 Changes
    * Change the shebang line in Perl scripts to look up perl in the PATH.