diff --git a/src/main/java/org/apache/xmlbeans/impl/schema/XsbReader.java b/src/main/java/org/apache/xmlbeans/impl/schema/XsbReader.java
index f03b95bd8..9094a2164 100644
--- a/src/main/java/org/apache/xmlbeans/impl/schema/XsbReader.java
+++ b/src/main/java/org/apache/xmlbeans/impl/schema/XsbReader.java
@@ -383,6 +383,7 @@ SchemaAnnotation readAnnotation(SchemaContainer c) {
         if (n == -1) {
             return null;
         }
+        checkAnnotationCount(n);
         SchemaAnnotation.Attribute[] attributes =
             new SchemaAnnotation.Attribute[n];
         for (int i = 0; i < n; i++) {
@@ -397,6 +398,7 @@ SchemaAnnotation readAnnotation(SchemaContainer c) {
 
         // Read documentation items
         n = readInt();
+        checkAnnotationCount(n);
         String[] docStrings = new String[n];
         for (int i = 0; i < n; i++) {
             docStrings[i] = readString();
@@ -404,6 +406,7 @@ SchemaAnnotation readAnnotation(SchemaContainer c) {
 
         // Read application info items
         n = readInt();
+        checkAnnotationCount(n);
         String[] appInfoStrings = new String[n];
         for (int i = 0; i < n; i++) {
             appInfoStrings[i] = readString();
@@ -422,6 +425,7 @@ void writeAnnotations(SchemaAnnotation[] anns) {
 
     List<SchemaAnnotation> readAnnotations() {
         int n = readInt();
+        checkAnnotationCount(n);
         List<SchemaAnnotation> result = new ArrayList<>(n);
         // BUGBUG(radup)
         SchemaContainer container = typeSystem.getContainerNonNull("");
@@ -431,6 +435,13 @@ List<SchemaAnnotation> readAnnotations() {
         return result;
     }
 
+    private void checkAnnotationCount(int n) {
+        if (n < 0) {
+            throw new SchemaTypeLoaderException("Invalid annotation count " + n,
+                typeSystem.getName(), _handle, SchemaTypeLoaderException.UNRECOGNIZED_INDEX_ENTRY);
+        }
+    }
+
     SchemaComponent.Ref readHandle() {
         String handle = readString();
         if (handle == null) {
diff --git a/src/test/java/org/apache/xmlbeans/impl/schema/XsbReaderAnnotationCountTest.java b/src/test/java/org/apache/xmlbeans/impl/schema/XsbReaderAnnotationCountTest.java
new file mode 100644
index 000000000..3a7086343
--- /dev/null
+++ b/src/test/java/org/apache/xmlbeans/impl/schema/XsbReaderAnnotationCountTest.java
@@ -0,0 +1,91 @@
+/*   Licensed to the Apache Software Foundation (ASF) under one or more
+ *   contributor license agreements.  See the NOTICE file distributed with
+ *   this work for additional information regarding copyright ownership.
+ *   The ASF licenses this file to You under the Apache License, Version 2.0
+ *   (the "License"); you may not use this file except in compliance with
+ *   the License.  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   Unless required by applicable law or agreed to in writing, software
+ *   distributed under the License is distributed on an "AS IS" BASIS,
+ *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *   See the License for the specific language governing permissions and
+ *   limitations under the License.
+ */
+
+package org.apache.xmlbeans.impl.schema;
+
+import org.apache.xmlbeans.SchemaTypeLoaderException;
+import org.apache.xmlbeans.impl.util.LongUTFDataInputStream;
+import org.junit.jupiter.api.Test;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.lang.reflect.Field;
+
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class XsbReaderAnnotationCountTest {
+
+    // Builds a reader whose next reads come from the given on-wire ints, exactly
+    // as a crafted/corrupt .xsb annotation section would supply them. When
+    // withVersion is set the version fields are bumped so readAnnotation gets
+    // past its atLeast(2, 19, 0) guard and reaches the count reads.
+    private static XsbReader reader(boolean withVersion, int... ints) throws Exception {
+        ByteArrayOutputStream bos = new ByteArrayOutputStream();
+        DataOutputStream dos = new DataOutputStream(bos);
+        for (int i : ints) {
+            dos.writeInt(i); // same on-wire form as XsbReader.writeInt
+        }
+        dos.flush();
+
+        XsbReader reader = new XsbReader(new SchemaTypeSystemImpl("test"), "h");
+        set(reader, "_input", new LongUTFDataInputStream(new ByteArrayInputStream(bos.toByteArray())));
+        if (withVersion) {
+            set(reader, "_majorver", SchemaTypeSystemImpl.MAJOR_VERSION);
+            set(reader, "_minorver", SchemaTypeSystemImpl.MINOR_VERSION);
+            set(reader, "_releaseno", SchemaTypeSystemImpl.RELEASE_NUMBER);
+        }
+        return reader;
+    }
+
+    private static void set(XsbReader reader, String name, Object value) throws Exception {
+        Field f = XsbReader.class.getDeclaredField(name);
+        f.setAccessible(true);
+        f.set(reader, value);
+    }
+
+    @Test
+    void readAnnotationsRejectsNegativeCount() throws Exception {
+        XsbReader reader = reader(false, -2);
+        assertThrows(SchemaTypeLoaderException.class, reader::readAnnotations);
+    }
+
+    @Test
+    void readAnnotationRejectsNegativeAttributeCount() throws Exception {
+        XsbReader reader = reader(true, -2);
+        assertThrows(SchemaTypeLoaderException.class, () -> reader.readAnnotation(null));
+    }
+
+    @Test
+    void readAnnotationRejectsNegativeDocumentationCount() throws Exception {
+        XsbReader reader = reader(true, 0, -2);
+        assertThrows(SchemaTypeLoaderException.class, () -> reader.readAnnotation(null));
+    }
+
+    @Test
+    void readAnnotationRejectsNegativeAppinfoCount() throws Exception {
+        XsbReader reader = reader(true, 0, 0, -2);
+        assertThrows(SchemaTypeLoaderException.class, () -> reader.readAnnotation(null));
+    }
+
+    // -1 is the null-annotation sentinel and must still be accepted unchanged.
+    @Test
+    void readAnnotationKeepsNullSentinel() throws Exception {
+        XsbReader reader = reader(true, -1);
+        assertNull(reader.readAnnotation(null));
+    }
+}