diff --git a/pom.xml b/pom.xml
index 04d2cf5..53ab717 100644
--- a/pom.xml
+++ b/pom.xml
@@ -20,23 +20,23 @@
     <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-api</artifactId>
-      <version>${slf4j.version}</version>
+      <version>1.7.30</version>
     </dependency>
     <dependency>
       <groupId>io.netty</groupId>
       <artifactId>netty-all</artifactId>
-      <version>${netty.version}</version>
+      <version>4.1.51.Final</version>
     </dependency>
     <dependency>
       <groupId>ch.qos.logback</groupId>
       <artifactId>logback-classic</artifactId>
-      <version>${logback.version}</version>
+      <version>1.3.15</version>
     </dependency>
 
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
-      <version>${junit.version}</version>
+      <version>4.13.1</version>
       <scope>test</scope>
     </dependency>
   </dependencies>