Add ChangeLog entry
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@@ -3,6 +3,11 @@
 = mbed TLS 1.3.x branch released xxxx-xx-xx
 
 Security
+   * Fixed unlimited overread of heap-based buffer in ssl_read().
+     The issue could only happen client-side with renegotiation enabled.
+     Could result in DoS (application crash) or information leak
+     (if the application layer sent data read from ssl_read()
+     back to the server or to a third party). Can be triggered remotely.
    * Add exponent blinding to RSA private operations as a countermeasure
      against side-channel attacks like the cache attack described in
      https://arxiv.org/abs/1702.08719v2.