Update change log

diff --git a/ChangeLog b/ChangeLog
index 305eef6..115f56e 100644
--- a/ChangeLog
+++ b/ChangeLog

@@ -2,6 +2,11 @@
 
 = mbed TLS x.x.x branch released xxxx-xx-xx
 
+Security
+   * Fix a potential memory leak in mbedtls_ssl_setup( ) function. An allocation
+     failure could leave an unreleased buffer. A handshake init failure would
+     lead to leaving two unreleased buffers.
+
 Features
    * Add new crypto primitives from RFC 7539: stream cipher Chacha20, one-time
      authenticator Poly1305 and AEAD construct Chacha20-Poly1305. Contributed by