diff --git a/ChangeLog b/ChangeLog
index 5e3b71a3e..a70d71c66 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -9,6 +9,13 @@ Security
      RSA decryption (i.e. ciphersuites whose name contains RSA but not
      (EC)DH(E)). Reported by Eyal Ronen, Robert Gillham, Daniel Genkin, Adi
      Shamir, David Wong and Yuval Yarom. CVE-2018-19608
+   * In mbedtls_mpi_write_binary(), don't leak the exact size of the number
+     via branching and memory access patterns. An attacker who could submit
+     a plaintext for RSA PKCS#1 v1.5 decryption but only observe the timing
+     of the decryption and not its result could nonetheless decrypt RSA
+     plaintexts and forge RSA signatures. Other asymmetric algorithms may
+     have been similarly vulnerable. Reported by Eyal Ronen, Robert Gillham,
+     Daniel Genkin, Adi Shamir, David Wong and Yuval Yarom.
 
 Bugfix
    * Fix failure in hmac_drbg in the benchmark sample application, when