diff --git a/src/java.xml/share/classes/com/sun/org/apache/xml/internal/serializer/ToStream.java b/src/java.xml/share/classes/com/sun/org/apache/xml/internal/serializer/ToStream.java
index fc01f006e97..7bff17a455f 100644
--- a/src/java.xml/share/classes/com/sun/org/apache/xml/internal/serializer/ToStream.java
+++ b/src/java.xml/share/classes/com/sun/org/apache/xml/internal/serializer/ToStream.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2025, Oracle and/or its affiliates. All rights reserved.
  */
 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
@@ -55,7 +55,7 @@ import org.xml.sax.SAXException;
  * serializers (xml, html, text ...) that write output to a stream.
  *
  * @xsl.usage internal
- * @LastModified: Mar 2022
+ * @LastModified: Feb 2025
  */
 abstract public class ToStream extends SerializerBase {
 
@@ -955,7 +955,7 @@ abstract public class ToStream extends SerializerBase {
         throws IOException, SAXException
     {
         int status = -1;
-        if (i + 1 >= end)
+        if (i + 1 >= end && m_highSurrogate == 0)
         {
             m_highSurrogate = c;
             return status;
diff --git a/test/jaxp/javax/xml/jaxp/unittest/transform/JDK8207760.java b/test/jaxp/javax/xml/jaxp/unittest/transform/JDK8207760.java
index 00c1b8a8e25..6055fa878bc 100644
--- a/test/jaxp/javax/xml/jaxp/unittest/transform/JDK8207760.java
+++ b/test/jaxp/javax/xml/jaxp/unittest/transform/JDK8207760.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2025, 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
@@ -41,10 +41,10 @@ import org.testng.annotations.DataProvider;
 
 /*
  * @test
+ * @bug 8207760 8349699
+ * @summary Verifies that a surrogate pair at the edge of a buffer is properly handled
  * @library /javax/xml/jaxp/libs /javax/xml/jaxp/unittest
  * @run testng/othervm transform.JDK8207760
- * @summary Verifies that a surrogate pair at the edge of a buffer is properly handled
- * @bug 8207760
  */
 public class JDK8207760 {
     final String xsl8207760 =
@@ -93,6 +93,14 @@ public class JDK8207760 {
         "\n" +
         "</xsl:stylesheet>";
 
+    final String xsl8349699 = """
+                <?xml version="1.0" encoding="UTF-8"?>
+                <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+                  <xsl:output encoding="UTF-8" method="text" />
+                  <xsl:template match="/"><xsl:apply-templates select="node()" /></xsl:template>
+                </xsl:stylesheet>
+                """;
+
     @DataProvider(name = "xsls")
     public Object[][] getDataBug8207760_cdata() {
         return new Object[][]{
@@ -101,6 +109,117 @@ public class JDK8207760 {
         };
     }
 
+    /*
+     * Data for verifying the patch for JDK8349699
+     * @see testBug8349699
+     */
+    @DataProvider(name = "surrogatePair")
+    public Object[][] getDataFor8349699() {
+        return new Object[][]{
+            // a surrogate pair in an XML element placed anywhere in a string
+            {getXML(1024, 1024, "<b>\uD835\uDF00</b>"), getString(1024, 1024, "\uD835\uDF00")},
+            {getXML(1023, 1023, "<b>\uD835\uDF00</b>"), getString(1023, 1023, "\uD835\uDF00")},
+            {getXML(1023,0, "<b>\uD835\uDF00</b>"), getString(1023,0, "\uD835\uDF00")},
+            {getXML(1023,120, "<b>\uD835\uDF00</b>"), getString(1023,120, "\uD835\uDF00")},
+            // this is the original test as demonstrated in the bug report
+            {getXML(1017,1017, "\uD835\uDF03\uD835\uDF00\uD835\uDF00<b>\uD835\uDF00</b>\uD835\uDF00"),
+                    getString(1017,1017, "\uD835\uDF03\uD835\uDF00\uD835\uDF00\uD835\uDF00\uD835\uDF00")},
+            {getXML(1017,0, "\uD835\uDF03\uD835\uDF00\uD835\uDF00<b>\uD835\uDF00</b>\uD835\uDF00"),
+                    getString(1017,0, "\uD835\uDF03\uD835\uDF00\uD835\uDF00\uD835\uDF00\uD835\uDF00")},
+            {getXML(1017,120, "\uD835\uDF03\uD835\uDF00\uD835\uDF00<b>\uD835\uDF00</b>\uD835\uDF00"),
+                    getString(1017,120, "\uD835\uDF03\uD835\uDF00\uD835\uDF00\uD835\uDF00\uD835\uDF00")},
+        };
+    }
+
+    /*
+     * Data for verifying the patch for JDK8349699
+     * @see testBug8349699N
+     */
+    @DataProvider(name = "invalidSurrogatePair")
+    public Object[][] getDataFor8349699N() {
+        return new Object[][]{
+                // invalid pair: high/high
+                {getXML(1024, 1024, "<b>\uD835\uD835</b>")},
+                {getXML(1023, 1023, "<b>\uD835\uD835</b>")},
+                {getXML(1023,0, "<b>\uD835\uD835</b>")},
+                {getXML(1023,120, "<b>\uD835\uD835</b>")},
+                // invalid pair: low/low
+                {getXML(1024, 1024, "<b>\uDF00\uDF00</b>")},
+                {getXML(1023, 1023, "<b>\uDF00\uDF00</b>")},
+                {getXML(1023,0, "<b>\uDF00\uDF00</b>")},
+                {getXML(1023,120, "<b>\uDF00\uDF00</b>")},
+                // invalid pair in the original test string
+                {getXML(1017,1017, "\uD835\uDF03\uD835\uDF00\uD835\uDF00<b>\uD835\uD835</b>\uD835\uDF00")},
+                {getXML(1017,0, "\uD835\uDF03\uD835\uDF00\uD835\uDF00<b>\uD835\uD835</b>\uD835\uDF00")},
+                {getXML(1017,120, "\uD835\uDF03\uD835\uDF00\uD835\uDF00<b>\uD835\uD835</b>\uD835\uDF00")},
+                {getXML(1017,1017, "\uD835\uDF03\uD835\uDF00\uD835\uDF00<b>\uDF00\uDF00</b>\uD835\uDF00")},
+                {getXML(1017,0, "\uD835\uDF03\uD835\uDF00\uD835\uDF00<b>\uDF00\uDF00</b>\uD835\uDF00")},
+                {getXML(1017,120, "\uD835\uDF03\uD835\uDF00\uD835\uDF00<b>\uDF00\uDF00</b>\uD835\uDF00")},
+        };
+    }
+
+    /*
+     * @bug 8349699
+     * Verifies that a surrogate pair at the edge of a buffer is properly handled
+     * when serializing into a Character section.
+     */
+    @Test(dataProvider = "surrogatePair")
+    public final void testBug8349699(String xml, String expected) throws Exception {
+        Transformer t = createTransformerFromInputstream(
+                new ByteArrayInputStream(xsl8349699.getBytes(StandardCharsets.UTF_8)));
+        StringWriter sw = new StringWriter();
+        t.transform(new StreamSource(new StringReader(xml)), new StreamResult(sw));
+        Assert.assertEquals(sw.toString(), expected);
+    }
+
+    /*
+     * @bug 8349699
+     * Verifies that invalid surrogate pairs are caught.
+     */
+    @Test(dataProvider = "invalidSurrogatePair")
+    public final void testBug8349699N(String xml) throws Exception {
+        Assert.assertThrows(TransformerException.class, () -> {
+            Transformer t = createTransformerFromInputstream(
+                    new ByteArrayInputStream(xsl8349699.getBytes(StandardCharsets.UTF_8)));
+            StringWriter sw = new StringWriter();
+            t.transform(new StreamSource(new StringReader(xml)), new StreamResult(sw));
+        });
+    }
+
+    /**
+     * Returns an XML with the input string inserted in a text of length 'len' at
+     * the position 'pos'.
+     * @param len the length of the text to be placed in the XML
+     * @param pos the position at which the input string will be inserted into the text
+     * @param input the input string
+     * @return an XML
+     */
+    private String getXML(int len, int pos, String input) {
+        StringBuilder sb = new StringBuilder("<?xml version=\"1.0\" ?><a>");
+        sb.append(getString(len, pos, input));
+        sb.append("</a>");
+        return sb.toString();
+    }
+
+    /**
+     * Returns a text string with the input string inserted at the specified position.
+     * @param len the length of the text to be returned
+     * @param pos the position at which the input string will be inserted into the text
+     * @param input the input string
+     * @return a text string
+     */
+    private String getString(int len, int pos, String input) {
+        StringBuilder sb = new StringBuilder();
+        if (pos == 0) {
+            sb.append(input).append("x".repeat(len));
+        } else if (pos == len) {
+            sb.append("x".repeat(len)).append(input);
+        } else {
+            sb.append("x".repeat(pos)).append(input).append("x".repeat(len - pos));
+        }
+        return sb.toString();
+    }
+
     /*
      * @bug 8207760
      * Verifies that a surrogate pair at the edge of a buffer is properly handled