diff --git a/ChangeLog b/ChangeLog
index 9ea55e1..ce3554c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,12 @@
 
 = mbed TLS x.x.x branch released xxxx-xx-xx
 
+Security
+   * Fix an issue in the X.509 module which could lead to a buffer overread
+     during certificate extensions parsing. In case of receiving malformed
+     input (extensions length field equal to 0), an illegal read of one byte
+     beyond the input buffer is made. Found and analyzed by Nathan Crandall.
+
 Bugfix
    * Fix compilation error on C++, because of a variable named new.
      Found and fixed by Hirotaka Niisato in #1783.