diff --git a/pkgs/applications/networking/browsers/firefox/packages.nix b/pkgs/applications/networking/browsers/firefox/packages.nix
index 35326631b94f..dd1a5ec56a41 100644
--- a/pkgs/applications/networking/browsers/firefox/packages.nix
+++ b/pkgs/applications/networking/browsers/firefox/packages.nix
@@ -94,10 +94,10 @@
 
   firefox-esr-128 = buildMozillaMach rec {
     pname = "firefox";
-    version = "128.3.0esr";
+    version = "128.3.1esr";
     src = fetchurl {
       url = "mirror://mozilla/firefox/releases/${version}/source/firefox-${version}.source.tar.xz";
-      sha512 = "3c6ef272c0fb653d030fe3f7f72aa0e1097b1c6759556166815cde15465330f988b3bc23df4b4eb753daee930edbb1ef72145273cb29d0952bd9d7c547050f9b";
+      sha512 = "c5c1a2e951e0dbb1259a0f77a26b8678bfa4a4c7e909f8fcd5c6d0f807625926824ed235e114d9bab5e289232efaaf4c6691764db64860161ebc9bece9200f0c";
     };
 
     meta = {