undefect. CWE-407 — 63 sites patched across 27 ecosystems

Authors: russell@unturf.com · brackishbert@gmail.com · foxhop.net · TimeHexOn.com

Patches, unit tests, benchmarks, whitepaper, and outreach briefs.
Public domain — no copyright claimed. Use freely.

test/jdk/java/io/DataOutputStream/WriteUTF.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 1999, 2026, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/* @test
+ * @bug 4260284 8219196 8223254
+ * @summary Test if DataOutputStream will overcount written field.
+ * @requires (sun.arch.data.model == "64" & os.maxMemory >= 4g)
+ * @run junit/othervm -Xmx4g WriteUTF
+ */
+
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.io.UTFDataFormatException;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class WriteUTF {
+    @Test
+    public void overcountWrittenField() throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        DataOutputStream dos = new DataOutputStream(baos);
+        dos.writeUTF("Hello, World!");  // 15
+        dos.flush();
+        if  (baos.size() != dos.size())
+            throw new RuntimeException("Miscounted bytes in DataOutputStream.");
+    }
+
+    private static void writeUTF(int size) throws IOException {
+        // this character gives 3 bytes when encoded using UTF-8
+        String s = "\u0800".repeat(size);
+        ByteArrayOutputStream bos = new ByteArrayOutputStream();
+        DataOutputStream dos = new DataOutputStream(bos);
+        dos.writeUTF(s);
+    }
+
+    @Test
+    public void utfDataFormatException() throws IOException {
+        assertThrows(UTFDataFormatException.class, () -> writeUTF(1 << 16));
+    }
+
+    // Without 8219196 fix, throws ArrayIndexOutOfBoundsException instead of
+    // expected UTFDataFormatException. Requires 4GB of heap (-Xmx4g) to run
+    // without throwing an OutOfMemoryError.
+    @Test
+    public void arrayIndexOutOfBoundsException() throws IOException {
+        assertThrows(UTFDataFormatException.class, () -> writeUTF(Integer.MAX_VALUE / 3 + 1));
+    }
+}