Add ChangeLog entry
diff --git a/ChangeLog b/ChangeLog
index 16982a0..ee020ab 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,12 @@
= mbed TLS 2.7.x branch released xxxx-xx-xx
+Security
+ * Fix side channel vulnerability in ECDSA key generation. Obtaining precise
+ timings on the comparison in the key generation enabled the attacker to
+ learn leading bits of the ephemeral key used during ECDSA signatures and to
+ recover the private key.
+
Changes
* Add unit tests for AES-GCM when called through mbedtls_cipher_auth_xxx()
from the cipher abstraction layer. Fixes #2198.