File logback-CVE-2026-1225.patch of Package logback.42520

--- a/logback-core/src/main/java/ch/qos/logback/core/joran/action/IADataForComplexProperty.java
+++ b/logback-core/src/main/java/ch/qos/logback/core/joran/action/IADataForComplexProperty.java
@@ -26,6 +26,7 @@ public class IADataForComplexProperty {
     final AggregationType aggregationType;
     final String complexPropertyName;
     private Object nestedComplexProperty;
+    private Class<?> expectedPropertyType;
     boolean inError;
 
     public IADataForComplexProperty(PropertySetter parentBean, AggregationType aggregationType, String complexPropertyName) {
@@ -46,6 +47,14 @@ public class IADataForComplexProperty {
         return complexPropertyName;
     }
 
+    public Class<?> getExpectedPropertyType() {
+        return expectedPropertyType;
+    }
+
+    public void setExpectedPropertyType(Class<?> expectedPropertyType) {
+        this.expectedPropertyType = expectedPropertyType;
+    }
+
     public void setNestedComplexProperty(Object nestedComplexProperty) {
         this.nestedComplexProperty = nestedComplexProperty;
     }
--- a/logback-core/src/main/java/ch/qos/logback/core/joran/action/NestedComplexPropertyIA.java
+++ b/logback-core/src/main/java/ch/qos/logback/core/joran/action/NestedComplexPropertyIA.java
@@ -76,7 +76,9 @@ public class NestedComplexPropertyIA extends ImplicitAction {
             // we only push action data if NestComponentIA is applicable
         case AS_COMPLEX_PROPERTY_COLLECTION:
         case AS_COMPLEX_PROPERTY:
+            Class<?> propertyType = parentBean.getTypeForComplexProperty(nestedElementTagName, aggregationType);
             IADataForComplexProperty ad = new IADataForComplexProperty(parentBean, aggregationType, nestedElementTagName);
+            ad.setExpectedPropertyType(propertyType);
             actionDataStack.push(ad);
 
             return true;
@@ -118,7 +120,11 @@ public class NestedComplexPropertyIA extends ImplicitAction {
                 addInfo("Assuming default type [" + componentClass.getName() + "] for [" + localName + "] property");
             }
 
-            actionData.setNestedComplexProperty(componentClass.newInstance());
+            Class<?> expectedPropertyType = actionData.getExpectedPropertyType();
+
+            Object object = OptionHelper.instantiateClassWithSuperclassRestriction(componentClass, expectedPropertyType);
+
+            actionData.setNestedComplexProperty(object);
 
             // pass along the repository
             if (actionData.getNestedComplexProperty() instanceof ContextAware) {
--- a/logback-core/src/main/java/ch/qos/logback/core/joran/util/PropertySetter.java
+++ b/logback-core/src/main/java/ch/qos/logback/core/joran/util/PropertySetter.java
@@ -395,4 +395,36 @@ public class PropertySetter extends ContextAwareBase {
         return getByConcreteType(name, relevantMethod);
     }
 
+    public Class<?> getTypeForComplexProperty(String nestedElementTagName, AggregationType aggregationType) {
+
+        Method aMethod = null;
+        switch (aggregationType) {
+            case AS_COMPLEX_PROPERTY:
+                aMethod = findSetterMethod(nestedElementTagName);
+                break;
+            case AS_COMPLEX_PROPERTY_COLLECTION:
+                aMethod = findAdderMethod(nestedElementTagName);
+        }
+
+
+        checkParameterCount(aMethod, nestedElementTagName);
+
+        Class<?>[] paramTypes = aMethod.getParameterTypes();
+        return paramTypes[0];
+
+    }
+
+    private void checkParameterCount(Method aMethod, String nestedElementTagName) {
+        if(aMethod == null) {
+            String msg = "Could not find method for property [" + nestedElementTagName + "].";
+            addError(msg);
+            throw new IllegalStateException(msg);
+        }
+        int parameterCount = aMethod.getParameterCount();
+        if (parameterCount != 1) {
+            String msg = "Expected ["+aMethod.getName()+"] for property [" + nestedElementTagName + "] to have exactly one parameter.";
+            addError(msg);
+            throw new IllegalStateException(msg);
+        }
+    }
 }
--- a/logback-core/src/main/java/ch/qos/logback/core/util/OptionHelper.java
+++ b/logback-core/src/main/java/ch/qos/logback/core/util/OptionHelper.java
@@ -14,6 +14,7 @@
 package ch.qos.logback.core.util;
 
 import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
 import java.util.Properties;
 
 import ch.qos.logback.core.Context;
@@ -44,6 +45,19 @@ public class OptionHelper {
         return instantiateByClassNameAndParameter(className, superClass, classLoader, null, null);
     }
 
+    public static Object instantiateClassWithSuperclassRestriction(Class<?> classObj, Class<?> superClass)
+            throws IncompatibleClassException, DynamicClassLoadingException {
+        if (!superClass.isAssignableFrom(classObj)) {
+            throw new IncompatibleClassException(superClass, classObj);
+        }
+
+        try {
+            return classObj.getConstructor().newInstance();
+        } catch (NoSuchMethodException|InstantiationException|IllegalAccessException|InvocationTargetException e) {
+            throw new DynamicClassLoadingException("Failed to instantiate type " + classObj.getName(), e);
+        }
+    }
+
     public static Object instantiateByClassNameAndParameter(String className, Class<?> superClass, ClassLoader classLoader, Class<?> type, Object parameter)
                     throws IncompatibleClassException, DynamicClassLoadingException {