Add changelog entry for the memory management fixes

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog.d/ecp-bignum-error-checks.txt b/ChangeLog.d/ecp-bignum-error-checks.txt
new file mode 100644
index 0000000..8cad08e
--- /dev/null
+++ b/ChangeLog.d/ecp-bignum-error-checks.txt
@@ -0,0 +1,5 @@
+Bugfix
+   * Fix a memory leak in mbedtls_mpi_sub_abs() when the result was negative
+     (an error condition) and the second operand was aliased to the result.
+   * Fix a case in elliptic curve arithmetic where an out-of-memory condition
+     could go undetected, resulting in an incorrect result.