diff --git a/logstash-core/build.gradle b/logstash-core/build.gradle
index de201dc6679..16f64367390 100644
--- a/logstash-core/build.gradle
+++ b/logstash-core/build.gradle
@@ -45,7 +45,14 @@ String jacksonVersion = versionMap['jackson']
 String jacksonDatabindVersion = versionMap['jackson-databind']
 String jrubyVersion = versionMap['jruby']['version']
 
-String log4jVersion = '2.17.2'
+String log4jVersion = '2.25.3'
+
+// Specifically call use of PluginProcessor to skip GraalVmProcessor (not needed)
+tasks.named('compileJava') {
+    options.compilerArgs.addAll([
+        "-processor", "org.apache.logging.log4j.core.config.plugins.processor.PluginProcessor"
+    ])
+}
 
 tasks.register("sourcesJar", Jar) {
     dependsOn classes
@@ -242,7 +249,7 @@ dependencies {
         exclude group: 'com.google.guava', module: 'guava'
     }
     implementation 'org.javassist:javassist:3.30.2-GA'
-    testImplementation "org.apache.logging.log4j:log4j-core:${log4jVersion}:tests"
+    testImplementation "org.apache.logging.log4j:log4j-core-test:${log4jVersion}"
     testImplementation 'org.hamcrest:hamcrest:2.2'
     testImplementation 'org.hamcrest:hamcrest-library:2.2'
     testImplementation 'junit:junit:4.13.2'
diff --git a/logstash-core/src/main/java/org/logstash/log/StructuredMessage.java b/logstash-core/src/main/java/org/logstash/log/StructuredMessage.java
index 9c0feee058c..e3d1c5816b0 100644
--- a/logstash-core/src/main/java/org/logstash/log/StructuredMessage.java
+++ b/logstash-core/src/main/java/org/logstash/log/StructuredMessage.java
@@ -88,6 +88,7 @@ public String getFormattedMessage() {
         return formatted;
     }
 
+    @SuppressWarnings("deprecation")
     @Override
     public String getFormat() {
         return null;
diff --git a/logstash-core/src/test/java/org/logstash/ObjectMappersTest.java b/logstash-core/src/test/java/org/logstash/ObjectMappersTest.java
index ad30631e798..994f03ad181 100644
--- a/logstash-core/src/test/java/org/logstash/ObjectMappersTest.java
+++ b/logstash-core/src/test/java/org/logstash/ObjectMappersTest.java
@@ -41,15 +41,22 @@ public void testLog4jOMRegisterRubyBasicObjectSerializersFirst() {
             list.add(serializer);
         }
 
-        // RubyBasicObjectSerializer + Log4jJsonModule
+        // RubyBasicObjectSerializer + Log4jJsonModule + potentially other modules
         assertTrue(list.size() > 1);
 
-        final Serializers rubyBasicObjectSerializer = list.get(list.size() - 2);
+        // Find the RubyBasicObjectSerializer among the registered serializers
         final JavaType valueType = TypeFactory.defaultInstance().constructType(RubyBasicObject.class);
-        final JsonSerializer<?> found = rubyBasicObjectSerializer.findSerializer(mapper.getSerializationConfig(), valueType, null);
+        JsonSerializer<?> found = null;
+        for (Serializers serializer : list) {
+            JsonSerializer<?> candidate = serializer.findSerializer(mapper.getSerializationConfig(), valueType, null);
+            if (candidate instanceof RubyBasicObjectSerializer) {
+                found = candidate;
+                break;
+            }
+        }
 
-        assertNotNull(found);
-        assertTrue("RubyBasicObjectSerializer must be registered before others non-default serializers", found instanceof RubyBasicObjectSerializer);
+        assertNotNull("RubyBasicObjectSerializer must be registered", found);
+        assertTrue("RubyBasicObjectSerializer must be registered", found instanceof RubyBasicObjectSerializer);
     }
 
     @Test
diff --git a/logstash-core/src/test/java/org/logstash/execution/ShutdownWatcherExtTest.java b/logstash-core/src/test/java/org/logstash/execution/ShutdownWatcherExtTest.java
index 79ca8ac0a5a..300bcae1060 100644
--- a/logstash-core/src/test/java/org/logstash/execution/ShutdownWatcherExtTest.java
+++ b/logstash-core/src/test/java/org/logstash/execution/ShutdownWatcherExtTest.java
@@ -35,8 +35,8 @@
 import java.util.stream.IntStream;
 import javax.annotation.concurrent.NotThreadSafe;
 
-import org.apache.logging.log4j.junit.LoggerContextRule;
-import org.apache.logging.log4j.test.appender.ListAppender;
+import org.apache.logging.log4j.core.test.junit.LoggerContextRule;
+import org.apache.logging.log4j.core.test.appender.ListAppender;
 import org.assertj.core.api.Assertions;
 import org.jruby.RubySystemExit;
 import org.jruby.exceptions.RaiseException;
diff --git a/logstash-core/src/test/java/org/logstash/jackson/StreamReadConstraintsUtilTest.java b/logstash-core/src/test/java/org/logstash/jackson/StreamReadConstraintsUtilTest.java
index 949d960dcc4..a8041aef0f8 100644
--- a/logstash-core/src/test/java/org/logstash/jackson/StreamReadConstraintsUtilTest.java
+++ b/logstash-core/src/test/java/org/logstash/jackson/StreamReadConstraintsUtilTest.java
@@ -3,8 +3,8 @@
 import com.fasterxml.jackson.core.StreamReadConstraints;
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.core.LogEvent;
-import org.apache.logging.log4j.junit.LoggerContextRule;
-import org.apache.logging.log4j.test.appender.ListAppender;
+import org.apache.logging.log4j.core.test.junit.LoggerContextRule;
+import org.apache.logging.log4j.core.test.appender.ListAppender;
 import org.junit.Before;
 import org.junit.ClassRule;
 import org.junit.Rule;
diff --git a/logstash-core/src/test/java/org/logstash/log/CustomLogEventTests.java b/logstash-core/src/test/java/org/logstash/log/CustomLogEventTests.java
index 5e5a4ce172f..d7d78c94cc6 100644
--- a/logstash-core/src/test/java/org/logstash/log/CustomLogEventTests.java
+++ b/logstash-core/src/test/java/org/logstash/log/CustomLogEventTests.java
@@ -48,8 +48,8 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.ThreadContext;
-import org.apache.logging.log4j.junit.LoggerContextRule;
-import org.apache.logging.log4j.test.appender.ListAppender;
+import org.apache.logging.log4j.core.test.junit.LoggerContextRule;
+import org.apache.logging.log4j.core.test.appender.ListAppender;
 import org.jruby.RubyHash;
 import org.jruby.runtime.builtin.IRubyObject;
 import org.junit.After;
diff --git a/logstash-core/src/test/java/org/logstash/log/LogstashConfigurationFactoryTest.java b/logstash-core/src/test/java/org/logstash/log/LogstashConfigurationFactoryTest.java
index 3399e314f1c..e646d8e5443 100644
--- a/logstash-core/src/test/java/org/logstash/log/LogstashConfigurationFactoryTest.java
+++ b/logstash-core/src/test/java/org/logstash/log/LogstashConfigurationFactoryTest.java
@@ -30,7 +30,7 @@
 import org.apache.logging.log4j.core.config.Configuration;
 
 import org.apache.logging.log4j.core.LoggerContext;
-import org.apache.logging.log4j.test.appender.ListAppender;
+import org.apache.logging.log4j.core.test.appender.ListAppender;
 import org.junit.*;
 
 import java.util.List;
diff --git a/logstash-core/src/test/java/org/logstash/log/PipelineRoutingAppenderTest.java b/logstash-core/src/test/java/org/logstash/log/PipelineRoutingAppenderTest.java
index 5b930992771..7510e4da2e0 100644
--- a/logstash-core/src/test/java/org/logstash/log/PipelineRoutingAppenderTest.java
+++ b/logstash-core/src/test/java/org/logstash/log/PipelineRoutingAppenderTest.java
@@ -5,9 +5,9 @@
 import org.apache.logging.log4j.core.LoggerContext;
 import org.apache.logging.log4j.core.config.AppenderControl;
 import org.apache.logging.log4j.core.config.Configuration;
-import org.apache.logging.log4j.junit.LoggerContextRule;
+import org.apache.logging.log4j.core.test.junit.LoggerContextRule;
 import org.apache.logging.log4j.message.StructuredDataMessage;
-import org.apache.logging.log4j.test.appender.ListAppender;
+import org.apache.logging.log4j.core.test.appender.ListAppender;
 import org.junit.After;
 import org.junit.Rule;
 import org.junit.Test;
@@ -38,6 +38,7 @@ public void tearDown() {
         this.loggerContextRule.getLoggerContext().stop();
     }
 
+    @SuppressWarnings("deprecation")
     @Test
     public void routingTest() {
         final String pipelineId = "test_pipeline";
diff --git a/logstash-core/src/test/java/org/logstash/settings/ValidatedPasswordSettingTest.java b/logstash-core/src/test/java/org/logstash/settings/ValidatedPasswordSettingTest.java
index f5b8efef38a..b313cd55891 100644
--- a/logstash-core/src/test/java/org/logstash/settings/ValidatedPasswordSettingTest.java
+++ b/logstash-core/src/test/java/org/logstash/settings/ValidatedPasswordSettingTest.java
@@ -19,8 +19,8 @@
 package org.logstash.settings;
 
 import co.elastic.logstash.api.Password;
-import org.apache.logging.log4j.junit.LoggerContextRule;
-import org.apache.logging.log4j.test.appender.ListAppender;
+import org.apache.logging.log4j.core.test.junit.LoggerContextRule;
+import org.apache.logging.log4j.core.test.appender.ListAppender;
 import org.junit.Before;
 import org.junit.ClassRule;
 import org.junit.Test;
diff --git a/qa/rspec/commands/base.rb b/qa/rspec/commands/base.rb
index c2af5ccede2..7fbcfab24c5 100644
--- a/qa/rspec/commands/base.rb
+++ b/qa/rspec/commands/base.rb
@@ -39,11 +39,13 @@ def exit_status
   end
 
   def execute(cmdline)
-    Open3.popen3(cmdline) do |stdin, stdout, stderr, wait_thr|
-      @stdout = stdout.read.chomp
-      @stderr = stderr.read.chomp
-      @exit_status = wait_thr.value.exitstatus
-    end
+    # use of capture3 gives us strings instead of raw io objects
+    # this helps not having to deal with IO streams being full
+    # and requiring multi threaded reading to prevent tests being blocked
+    @stdout, @stderr, status = Open3.capture3(cmdline)
+    @stdout.chomp!
+    @stderr.chomp!
+    @exit_status = status.exitstatus
   end
 end