diff --git a/CMakeLists.txt b/CMakeLists.txt
index 01d0aaf3..d9a86362 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -11,7 +11,7 @@ project(mosquitto)
 cmake_minimum_required(VERSION 2.8)
 # Only for version 3 and up. cmake_policy(SET CMP0042 NEW)
 
-set (VERSION 1.5.2)
+set (VERSION 1.5.3)
 
 add_definitions (-DCMAKE -DVERSION=\"${VERSION}\")
 
diff --git a/ChangeLog.txt b/ChangeLog.txt
index 6651a0fe..18c5514d 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -1,6 +1,11 @@
-1.5.3 - 201810xx
+1.5.3 - 20180925
 ================
 
+Security:
+- Fix CVE-2018-12543. If a message is sent to Mosquitto with a topic that
+  begins with $, but is not $SYS, then an assert that should be unreachable is
+  triggered and Mosquitto will exit.
+
 Broker:
 - Elevate log level to warning for situation when socket limit is hit.
 - Remove requirement to use `user root` in snap package config files.
diff --git a/config.mk b/config.mk
index 96052346..46ffb6db 100644
--- a/config.mk
+++ b/config.mk
@@ -102,7 +102,7 @@ WITH_BUNDLED_DEPS:=yes
 
 # Also bump lib/mosquitto.h, CMakeLists.txt,
 # installer/mosquitto.nsi, installer/mosquitto64.nsi
-VERSION=1.5.2
+VERSION=1.5.3
 
 # Client library SO version. Bump if incompatible API/ABI changes are made.
 SOVERSION=1
diff --git a/installer/mosquitto.nsi b/installer/mosquitto.nsi
index 3774a511..b97f6f3a 100644
--- a/installer/mosquitto.nsi
+++ b/installer/mosquitto.nsi
@@ -9,7 +9,7 @@
 !define env_hklm 'HKLM "SYSTEM\CurrentControlSet\Control\Session Manager\Environment"'
 
 Name "Eclipse Mosquitto"
-!define VERSION 1.5.2
+!define VERSION 1.5.3
 OutFile "mosquitto-${VERSION}-install-windows-x86.exe"
 
 InstallDir "$PROGRAMFILES\mosquitto"
diff --git a/installer/mosquitto64.nsi b/installer/mosquitto64.nsi
index 44b2d9c6..59acea1a 100644
--- a/installer/mosquitto64.nsi
+++ b/installer/mosquitto64.nsi
@@ -9,7 +9,7 @@
 !define env_hklm 'HKLM "SYSTEM\CurrentControlSet\Control\Session Manager\Environment"'
 
 Name "Eclipse Mosquitto"
-!define VERSION 1.5.2
+!define VERSION 1.5.3
 OutFile "mosquitto-${VERSION}-install-windows-x64.exe"
 
 !include "x64.nsh"
diff --git a/lib/mosquitto.h b/lib/mosquitto.h
index 100ea1a6..3d15666d 100644
--- a/lib/mosquitto.h
+++ b/lib/mosquitto.h
@@ -47,7 +47,7 @@ extern "C" {
 
 #define LIBMOSQUITTO_MAJOR 1
 #define LIBMOSQUITTO_MINOR 5
-#define LIBMOSQUITTO_REVISION 2
+#define LIBMOSQUITTO_REVISION 3
 /* LIBMOSQUITTO_VERSION_NUMBER looks like 1002001 for e.g. version 1.2.1. */
 #define LIBMOSQUITTO_VERSION_NUMBER (LIBMOSQUITTO_MAJOR*1000000+LIBMOSQUITTO_MINOR*1000+LIBMOSQUITTO_REVISION)
 
diff --git a/set-version.sh b/set-version.sh
index d504a0bf..522dfa1d 100755
--- a/set-version.sh
+++ b/set-version.sh
@@ -2,7 +2,7 @@
 
 MAJOR=1
 MINOR=5
-REVISION=2
+REVISION=3
 
 sed -i "s/^VERSION=.*/VERSION=${MAJOR}.${MINOR}.${REVISION}/" config.mk
 
diff --git a/snap/snapcraft.yaml b/snap/snapcraft.yaml
index fa941d80..c7569010 100644
--- a/snap/snapcraft.yaml
+++ b/snap/snapcraft.yaml
@@ -1,5 +1,5 @@
 name: mosquitto
-version: 1.5.2
+version: 1.5.3
 summary: Eclipse Mosquitto MQTT broker
 description: This is a message broker that supports version 3.1 and 3.1.1 of the MQTT
     protocol.