adding changelog entry for issue #4093

Signed-off-by: Daniel Otte <d.otte@wut.de>
diff --git a/ChangeLog.d/issue4093.txt b/ChangeLog.d/issue4093.txt
new file mode 100644
index 0000000..b8d634b
--- /dev/null
+++ b/ChangeLog.d/issue4093.txt
@@ -0,0 +1,7 @@
+Security
+   * Fix an errorneous estimation for an internal buffer in
+     mbedtls_pk_write_key_pem(). If MBEDTLS_MPI_MAX_SIZE is set to an odd
+     value the function might fail to write a private RSA keys of the largest
+     supported size.
+     Found by Daniel Otte, reported in #4093 and fixed in #4094,
+     backported in #4100.