Fix #4403: prevent use of zero-prefixed String as Enum index on deserialization

release-notes/VERSION-2.x

@@ -45,6 +45,8 @@ Project: jackson-databind
 #4394: Better Base64 support for `java.util.UUIDs`
   without padding
  (fix contributed by Jesper B)
+#4403: Deserialization of unknown value for enums does not yield default enum value
+ (reported by @dominik-henning)
 #4416: Deprecate `JsonNode.asText(String)`
  (suggested by András P)
 - JUnit5 upgraded to 5.10.1

src/main/java/com/fasterxml/jackson/databind/deser/std/EnumDeserializer.java

@@ -415,18 +415,25 @@ private final Object _deserializeAltString(JsonParser p, DeserializationContext
                 // [databind#149]: Allow use of 'String' indexes as well -- unless prohibited (as per above)
                 char c = name.charAt(0);
                 if (c >= '0' && c <= '9') {
-                    try {
-                        int index = Integer.parseInt(name);
-                        if (!ctxt.isEnabled(MapperFeature.ALLOW_COERCION_OF_SCALARS)) {
-                            return ctxt.handleWeirdStringValue(_enumClass(), name,
+                    // [databind#4403]: cannot prevent "Stringified" numbers as Enum
+                    // index yet (might need combination of "Does format have Numbers"
+                    // (XML does not f.ex) and new `EnumFeature`. But can disallow "001" etc.
+                    if (c == '0' && name.length() > 1) {
+                        ;
+                    } else {
+                        try {
+                            int index = Integer.parseInt(name);
+                            if (!ctxt.isEnabled(MapperFeature.ALLOW_COERCION_OF_SCALARS)) {
+                                return ctxt.handleWeirdStringValue(_enumClass(), name,
 "value looks like quoted Enum index, but `MapperFeature.ALLOW_COERCION_OF_SCALARS` prevents use"
-                                    );
+                                        );
+                            }
+                            if (index >= 0 && index < _enumsByIndex.length) {
+                                return _enumsByIndex[index];
+                            }
+                        } catch (NumberFormatException e) {
+                            // fine, ignore, was not an integer
                         }
-                        if (index >= 0 && index < _enumsByIndex.length) {
-                            return _enumsByIndex[index];
-                        }
-                    } catch (NumberFormatException e) {
-                        // fine, ignore, was not an integer
                     }
                 }
             }

src/test/java/com/fasterxml/jackson/failing/EnumDefaultRead4403Test.java → src/test/java/com/fasterxml/jackson/databind/deser/enums/EnumDefaultRead4403Test.java

@@ -1,4 +1,4 @@
-package com.fasterxml.jackson.failing;
+package com.fasterxml.jackson.databind.deser.enums;
 
 import org.junit.jupiter.api.Test;