diff --git a/test-framework/junit5-internal/src/main/java/io/quarkus/test/ConfigUtil.java b/test-framework/junit5-internal/src/main/java/io/quarkus/test/ConfigUtil.java
new file mode 100644
index 0000000000000..c7c0c5ebc1488
--- /dev/null
+++ b/test-framework/junit5-internal/src/main/java/io/quarkus/test/ConfigUtil.java
@@ -0,0 +1,30 @@
+package io.quarkus.test;
+
+import io.quarkus.runtime.configuration.QuarkusConfigFactory;
+
+public final class ConfigUtil {
+    private ConfigUtil() {
+    }
+
+    /**
+     * Clean up config left over from badly-behaving previous tests.
+     * <p>
+     * Tests may call ConfigProvider.getConfig() directly or indirectly,
+     * triggering lazy initialization in QuarkusConfigFactory#getConfigFor,
+     * and if they don't call QuarkusConfigFactory.setConfig(null) afterward,
+     * they may leak that config.
+     * As it's quite hard to guarantee that all tests clean up after them,
+     * especially if they don't use any Quarkus*Test extensions,
+     * we call this cleanup here in Quarkus*Test extensions as an additional safeguard.
+     * <p>
+     * Note this must be called quite early in extensions in order to be effective:
+     * things like TestHTTPResourceManager#getUri make use of config and may be called very early,
+     * upon test instantiation, so cleaning up in beforeEach() won't cut it for example.
+     */
+    public static void cleanUp() {
+        try {
+            QuarkusConfigFactory.setConfig(null);
+        } catch (Throwable ignored) {
+        }
+    }
+}
diff --git a/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusDevModeTest.java b/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusDevModeTest.java
index c80f987df6caf..79cc8f6b2c1b7 100644
--- a/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusDevModeTest.java
+++ b/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusDevModeTest.java
@@ -228,6 +228,7 @@ public Object createTestInstance(TestInstanceFactoryContext factoryContext, Exte
 
     @Override
     public void beforeAll(ExtensionContext context) throws Exception {
+        ConfigUtil.cleanUp();
         GroovyClassValue.disable();
         //set the right launch mode in the outer CL, used by the HTTP host config source
         ProfileManager.setLaunchMode(LaunchMode.DEVELOPMENT);
@@ -324,6 +325,7 @@ public void afterAll(ExtensionContext context) throws Exception {
         inMemoryLogHandler.clearRecords();
         inMemoryLogHandler.setFilter(null);
         ClearCache.clearAnnotationCache();
+        ConfigUtil.cleanUp();
     }
 
     @Override
diff --git a/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusProdModeTest.java b/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusProdModeTest.java
index 3e5b7c72ef43f..936ce48d4cb6e 100644
--- a/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusProdModeTest.java
+++ b/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusProdModeTest.java
@@ -365,6 +365,7 @@ private JavaArchive getArchiveProducerOrDefault() {
 
     @Override
     public void beforeAll(ExtensionContext extensionContext) throws Exception {
+        ConfigUtil.cleanUp();
         ensureNoInjectAnnotationIsUsed(extensionContext.getRequiredTestClass());
         ExclusivityChecker.checkTestType(extensionContext, QuarkusProdModeTest.class);
 
@@ -757,6 +758,8 @@ public void afterAll(ExtensionContext extensionContext) throws Exception {
             if ((outputDir != null) && !preventOutputDirCleanup) {
                 FileUtil.deleteDirectory(outputDir);
             }
+
+            ConfigUtil.cleanUp();
         }
     }
 
diff --git a/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusUnitTest.java b/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusUnitTest.java
index f17fd2e19514c..53c82ed45d735 100644
--- a/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusUnitTest.java
+++ b/test-framework/junit5-internal/src/main/java/io/quarkus/test/QuarkusUnitTest.java
@@ -507,6 +507,7 @@ private void runExtensionMethod(ReflectiveInvocationContext<Method> invocationCo
 
     @Override
     public void beforeAll(ExtensionContext extensionContext) throws Exception {
+        ConfigUtil.cleanUp();
         GroovyClassValue.disable();
         //set the right launch mode in the outer CL, used by the HTTP host config source
         ProfileManager.setLaunchMode(LaunchMode.TEST);
@@ -766,6 +767,7 @@ public void afterAll(ExtensionContext extensionContext) throws Exception {
                 afterAllCustomizer.run();
             }
             ClearCache.clearAnnotationCache();
+            ConfigUtil.cleanUp();
         }
         if (records != null) {
             assertLogRecords.accept(records);