Update document with 1.3.1 content

Change-Id: I8fc73212b2e553ded9fdb6d4f7d23d123c3e4e11
diff --git a/release/1.3.rst b/release/1.3.rst
index e5755d5..e1f18c6 100644
--- a/release/1.3.rst
+++ b/release/1.3.rst
@@ -124,3 +124,19 @@
 
     * 5g-ran-sim ``0.6.5``
         * gnbsim: ``omecproject/5gc-gnbsim:main-1caccfc``
+
+1.3.1 Release Details
+---------------------
+
+Minor release with bug fixes on top of release 1.3.0. Below is the list of defects fixed on top of previous release.
+
+    * SMF crash fix while allocating and releasing IP address
+
+Helm Chart Versions and their component charts versions
+
+* sdcore-helm-chart: ``0.12.9``
+    * omec-control-plane: ``0.12.0``
+    * omec-sub-provision: ``0.6.0``
+    * 5g-control-plane: ``0.8.16``
+    * bess-upf ``0.1.0``
+    * 5g-ran-sim ``0.6.5``