diff --git a/ChangeLog.d/dtls-cid-null.txt b/ChangeLog.d/dtls-cid-null.txt
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+Bugfix
+   * In configurations with MBEDTLS_SSL_DTLS_CONNECTION_ID enabled but not
+     MBEDTLS_DEBUG_C, DTLS handshakes using CID would crash due to a null
+     pointer dereference. Fix this. Fixes #3998.
+     The fix was released, but not announced, in Mbed TLS 3.1.0.