diff --git a/contribs/hybridsim/pom.xml b/contribs/hybridsim/pom.xml
index bed620d598d..d8f69b28046 100644
--- a/contribs/hybridsim/pom.xml
+++ b/contribs/hybridsim/pom.xml
@@ -10,7 +10,7 @@
 	<name>hybridsim</name>
 
 	<properties>
-		<protobuf.version>4.28.0</protobuf.version>
+		<protobuf.version>4.28.3</protobuf.version>
 		<grpc.version>1.66.0</grpc.version>
 	</properties>
 
diff --git a/contribs/protobuf/pom.xml b/contribs/protobuf/pom.xml
index 1a56905386a..53542aa2494 100644
--- a/contribs/protobuf/pom.xml
+++ b/contribs/protobuf/pom.xml
@@ -11,7 +11,7 @@
     <name>protobuf</name>
 
     <properties>
-        <protobuf.version>4.28.2</protobuf.version>
+        <protobuf.version>4.28.3</protobuf.version>
     </properties>
 
     <dependencies>