diff --git a/docs/changelog/110045.yaml b/docs/changelog/110045.yaml
new file mode 100644
index 0000000000000..01f8cf6551b16
--- /dev/null
+++ b/docs/changelog/110045.yaml
@@ -0,0 +1,6 @@
+pr: 110045
+summary: fix ignore_malformed behaviour for unsigned long fields
+area: Logs
+type: bug
+issues:
+ - 109705
diff --git a/x-pack/plugin/mapper-unsigned-long/src/main/java/org/elasticsearch/xpack/unsignedlong/UnsignedLongFieldMapper.java b/x-pack/plugin/mapper-unsigned-long/src/main/java/org/elasticsearch/xpack/unsignedlong/UnsignedLongFieldMapper.java
index eae4094fee0d0..e162886460bdc 100644
--- a/x-pack/plugin/mapper-unsigned-long/src/main/java/org/elasticsearch/xpack/unsignedlong/UnsignedLongFieldMapper.java
+++ b/x-pack/plugin/mapper-unsigned-long/src/main/java/org/elasticsearch/xpack/unsignedlong/UnsignedLongFieldMapper.java
@@ -626,7 +626,18 @@ protected void parseCreateField(DocumentParserContext context) throws IOExceptio
             numericValue = null;
         } else {
             try {
-                if (parser.currentToken() == XContentParser.Token.VALUE_NUMBER) {
+                if (parser.currentToken().isValue() == false) {
+                    if (ignoreMalformed.value()) {
+                        context.addIgnoredField(mappedFieldType.name());
+                        if (isSourceSynthetic) {
+                            context.doc().add(IgnoreMalformedStoredValues.storedField(fullPath(), context.parser()));
+                        }
+                        // NOTE: make sure we parse till the end to avoid the parser ends up in an illegal state
+                        parser.skipChildren();
+                        return;
+                    }
+                    numericValue = parseUnsignedLong(parser.text());
+                } else if (parser.currentToken() == XContentParser.Token.VALUE_NUMBER) {
                     numericValue = parseUnsignedLong(parser.numberValue());
                 } else {
                     numericValue = parseUnsignedLong(parser.text());
@@ -635,7 +646,6 @@ protected void parseCreateField(DocumentParserContext context) throws IOExceptio
                 if (ignoreMalformed.value() && parser.currentToken().isValue()) {
                     context.addIgnoredField(mappedFieldType.name());
                     if (isSourceSynthetic) {
-                        // Save a copy of the field so synthetic source can load it
                         context.doc().add(IgnoreMalformedStoredValues.storedField(fullPath(), context.parser()));
                     }
                     return;
diff --git a/x-pack/plugin/mapper-unsigned-long/src/yamlRestTest/resources/rest-api-spec/test/80_ignore_malformed.yml b/x-pack/plugin/mapper-unsigned-long/src/yamlRestTest/resources/rest-api-spec/test/80_ignore_malformed.yml
new file mode 100644
index 0000000000000..ae2984db41f64
--- /dev/null
+++ b/x-pack/plugin/mapper-unsigned-long/src/yamlRestTest/resources/rest-api-spec/test/80_ignore_malformed.yml
@@ -0,0 +1,262 @@
+---
+"unsigned_long with ignore_malformed in synthetic source":
+  - do:
+      indices.create:
+        index: test-synthetic
+        body:
+          mappings:
+            _source:
+              mode: synthetic
+            properties:
+              ul_ignored:
+                type: unsigned_long
+                ignore_malformed: true
+              ul_not_ignored:
+                type: unsigned_long
+                ignore_malformed: false
+
+  - do:
+      catch: bad_request
+      index:
+        refresh: true
+        index: test-synthetic
+        id: "1"
+        body: { "ul_ignored": 2000, "ul_not_ignored": { "key": "bar", value: 200 } }
+
+  - match: { error.root_cause.0.type: "document_parsing_exception" }
+
+  - do:
+      index:
+        refresh: true
+        index: test-synthetic
+        id: "2"
+        body: { "ul_ignored": { "key": "foo", "value": 100 }, "ul_not_ignored": 1000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-synthetic
+        id: "3"
+        body: { "ul_ignored": [ 100, 200, 300 ], "ul_not_ignored": 3000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-synthetic
+        id: "4"
+        body: { "ul_ignored": [ { "key": "a", "value": 100 }, { "key": "b", "value": 200 } ], "ul_not_ignored": 4000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-synthetic
+        id: "5"
+        body: { "ul_ignored": [1, { "key": "foo", "value": "bar" }, 3], "ul_not_ignored": 4000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-synthetic
+        id: "6"
+        body: { "ul_ignored": [ 1, "foo", 3, "bar" ], "ul_not_ignored": 4000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-synthetic
+        id: "7"
+        body: { "ul_not_ignored": 7000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-synthetic
+        id: "8"
+        body: { "ul_ignored": "", "ul_not_ignored": 8000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-synthetic
+        id: "9"
+        body: { "ul_ignored": "    ", "ul_not_ignored": 9000 }
+
+  - do:
+      search:
+        index: test-synthetic
+        body:
+          query:
+            match_all: { }
+
+  - match: { hits.total.value: 8 }
+
+  - match: { hits.hits.0._id: "2" }
+  - match: { hits.hits.0._source.ul_ignored: { "key": "foo", "value": 100 } }
+  - match: { hits.hits.0._source.ul_not_ignored: 1000 }
+  - match: { hits.hits.0._ignored.0: "ul_ignored" }
+
+  - match: { hits.hits.1._id: "3" }
+  - match: { hits.hits.1._source.ul_ignored: [ 100, 200, 300 ] }
+  - match: { hits.hits.1._source.ul_not_ignored: 3000 }
+  - match: { hits.hits.1._ignored: null }
+
+  - match: { hits.hits.2._id: "4" }
+  - match: { hits.hits.2._source.ul_ignored: [ { "key": "a", "value": 100 }, { "key": "b", "value": 200 } ] }
+  - match: { hits.hits.2._source.ul_not_ignored: 4000 }
+  - match: { hits.hits.2._ignored.0: "ul_ignored" }
+
+  - match: { hits.hits.3._id: "5" }
+  # NOTE: values sorting is different due to synthetic source using doc values
+  - match: { hits.hits.3._source.ul_ignored: [ 1, 3, { "key": "foo", "value": "bar" } ] }
+  - match: { hits.hits.3._source.ul_not_ignored: 4000 }
+  - match: { hits.hits.3._ignored.0: "ul_ignored" }
+
+  - match: { hits.hits.4._id: "6" }
+  # NOTE: values sorting is different due to synthetic source using doc values
+  - match: { hits.hits.4._source.ul_ignored: [ 1, 3, "foo", "bar" ] }
+  - match: { hits.hits.4._source.ul_not_ignored: 4000 }
+  - match: { hits.hits.4._ignored.0: "ul_ignored" }
+
+  - match: { hits.hits.5._id: "7" }
+  - match: { hits.hits.5._source.ul_ignored: null }
+  - match: { hits.hits.5._source.ul_not_ignored: 7000 }
+
+  - match: { hits.hits.6._id: "8" }
+  # NOTE: empty string treated as null value
+  - match: { hits.hits.6._source.ul_ignored: null }
+  - match: { hits.hits.6._source.ul_not_ignored: 8000 }
+
+  - match: { hits.hits.7._id: "9" }
+  - match: { hits.hits.7._source.ul_ignored: "    " }
+  - match: { hits.hits.7._source.ul_not_ignored: 9000 }
+  - match: { hits.hits.7._ignored.0: "ul_ignored" }
+
+---
+"unsigned_long with ignore_malformed with stored source":
+  - do:
+      indices.create:
+        index: test-stored
+        body:
+          mappings:
+            _source:
+              mode: stored
+            properties:
+              ul_ignored:
+                type: unsigned_long
+                ignore_malformed: true
+              ul_not_ignored:
+                type: unsigned_long
+                ignore_malformed: false
+
+  - do:
+      catch: bad_request
+      index:
+        refresh: true
+        index: test-stored
+        id: "1"
+        body: { "ul_ignored": 2000, "ul_not_ignored": { "key": "bar", value: 200 } }
+
+  - match: { error.root_cause.0.type: "document_parsing_exception" }
+
+  - do:
+      index:
+        refresh: true
+        index: test-stored
+        id: "2"
+        body: { "ul_ignored": { "key": "foo", "value": 100 }, "ul_not_ignored": 1000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-stored
+        id: "3"
+        body: { "ul_ignored": [ 100, 200, 300 ], "ul_not_ignored": 3000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-stored
+        id: "4"
+        body: { "ul_ignored": [ { "key": "a", "value": 100 }, { "key": "b", "value": 200 } ], "ul_not_ignored": 4000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-stored
+        id: "5"
+        body: { "ul_ignored": [1, { "key": "foo", "value": "bar" }, 3], "ul_not_ignored": 4000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-stored
+        id: "6"
+        body: { "ul_ignored": [ 1, "foo", 3, "bar" ], "ul_not_ignored": 4000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-stored
+        id: "7"
+        body: { "ul_not_ignored": 7000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-stored
+        id: "8"
+        body: { "ul_ignored": "", "ul_not_ignored": 8000 }
+
+  - do:
+      index:
+        refresh: true
+        index: test-stored
+        id: "9"
+        body: { "ul_ignored": "    ", "ul_not_ignored": 9000 }
+
+  - do:
+      search:
+        index: test-stored
+        body:
+          query:
+            match_all: { }
+
+  - match: { hits.total.value: 8 }
+
+  - match: { hits.hits.0._id: "2" }
+  - match: { hits.hits.0._source.ul_ignored: { "key": "foo", "value": 100 } }
+  - match: { hits.hits.0._source.ul_not_ignored: 1000 }
+  - match: { hits.hits.0._ignored.0: "ul_ignored" }
+
+  - match: { hits.hits.1._id: "3" }
+  - match: { hits.hits.1._source.ul_ignored: [ 100, 200, 300 ] }
+  - match: { hits.hits.1._source.ul_not_ignored: 3000 }
+  - match: { hits.hits.1._ignored: null }
+
+  - match: { hits.hits.2._id: "4" }
+  - match: { hits.hits.2._source.ul_ignored: [ { "key": "a", "value": 100 }, { "key": "b", "value": 200 } ] }
+  - match: { hits.hits.2._source.ul_not_ignored: 4000 }
+  - match: { hits.hits.2._ignored.0: "ul_ignored" }
+
+  - match: { hits.hits.3._id: "5" }
+  - match: { hits.hits.3._source.ul_ignored: [ 1, { "key": "foo", "value": "bar" }, 3 ] }
+  - match: { hits.hits.3._source.ul_not_ignored: 4000 }
+  - match: { hits.hits.3._ignored.0: "ul_ignored" }
+
+  - match: { hits.hits.4._id: "6" }
+  - match: { hits.hits.4._source.ul_ignored: [ 1, "foo", 3, "bar" ] }
+  - match: { hits.hits.4._source.ul_not_ignored: 4000 }
+  - match: { hits.hits.4._ignored.0: "ul_ignored" }
+
+  - match: { hits.hits.5._id: "7" }
+  - match: { hits.hits.5._source.ul_ignored: null }
+  - match: { hits.hits.5._source.ul_not_ignored: 7000 }
+
+  - match: { hits.hits.6._id: "8" }
+  - match: { hits.hits.6._source.ul_ignored: "" }
+  - match: { hits.hits.6._source.ul_not_ignored: 8000 }
+
+  - match: { hits.hits.7._id: "9" }
+  - match: { hits.hits.7._source.ul_ignored: "    " }
+  - match: { hits.hits.7._source.ul_not_ignored: 9000 }
+  - match: { hits.hits.7._ignored.0: "ul_ignored" }