diff --git a/services/cloudfront/pom.xml b/services/cloudfront/pom.xml
index 82ab05f9e456..624983098122 100644
--- a/services/cloudfront/pom.xml
+++ b/services/cloudfront/pom.xml
@@ -51,6 +51,11 @@
             <artifactId>aws-xml-protocol</artifactId>
             <version>${awsjavasdk.version}</version>
         </dependency>
+        <dependency>
+            <groupId>software.amazon.awssdk</groupId>
+            <artifactId>json-utils</artifactId>
+            <version>${awsjavasdk.version}</version>
+        </dependency>
         <dependency>
             <groupId>software.amazon.awssdk</groupId>
             <artifactId>protocol-core</artifactId>
diff --git a/services/cloudfront/src/main/java/software/amazon/awssdk/services/cloudfront/internal/utils/SigningUtils.java b/services/cloudfront/src/main/java/software/amazon/awssdk/services/cloudfront/internal/utils/SigningUtils.java
index 407ecec7088d..4b99ae619b3d 100644
--- a/services/cloudfront/src/main/java/software/amazon/awssdk/services/cloudfront/internal/utils/SigningUtils.java
+++ b/services/cloudfront/src/main/java/software/amazon/awssdk/services/cloudfront/internal/utils/SigningUtils.java
@@ -34,6 +34,7 @@
 import java.util.Base64;
 import software.amazon.awssdk.annotations.SdkInternalApi;
 import software.amazon.awssdk.core.exception.SdkClientException;
+import software.amazon.awssdk.protocols.jsoncore.JsonWriter;
 import software.amazon.awssdk.services.cloudfront.internal.auth.Pem;
 import software.amazon.awssdk.utils.IoUtils;
 import software.amazon.awssdk.utils.StringUtils;
@@ -57,11 +58,29 @@ private SigningUtils() {
      * >Setting signed cookies using a canned policy</a>.
      */
     public static String buildCannedPolicy(String resourceUrl, Instant expirationDate) {
-        return "{\"Statement\":[{\"Resource\":\""
-               + resourceUrl
-               + "\",\"Condition\":{\"DateLessThan\":{\"AWS:EpochTime\":"
-               + expirationDate.getEpochSecond()
-               + "}}}]}";
+        Validate.notNull(resourceUrl, "resourceUrl must not be null");
+        Validate.notNull(expirationDate, "expirationDate must not be null");
+        validateInput(resourceUrl, "resourceUrl");
+
+        JsonWriter writer = JsonWriter.create();
+        writer.writeStartObject()
+              .writeFieldName("Statement")
+              .writeStartArray()
+              .writeStartObject()
+              .writeFieldName("Resource")
+              .writeValue(resourceUrl)
+              .writeFieldName("Condition")
+              .writeStartObject()
+              .writeFieldName("DateLessThan")
+              .writeStartObject()
+              .writeFieldName("AWS:EpochTime")
+              .writeValue(expirationDate.getEpochSecond())
+              .writeEndObject()
+              .writeEndObject()
+              .writeEndObject()
+              .writeEndArray()
+              .writeEndObject();
+        return new String(writer.getBytes(), UTF_8);
     }
 
     /**
@@ -75,24 +94,72 @@ public static String buildCannedPolicy(String resourceUrl, Instant expirationDat
      * >Setting signed cookies using a custom policy</a>.
      */
     public static String buildCustomPolicy(String resourceUrl, Instant activeDate, Instant expirationDate,
-                                            String ipAddress) {
-        return "{\"Statement\": [{"
-               + "\"Resource\":\""
-               + resourceUrl
-               + "\""
-               + ",\"Condition\":{"
-               + "\"DateLessThan\":{\"AWS:EpochTime\":"
-               + expirationDate.getEpochSecond()
-               + "}"
-               + (ipAddress == null
-                  ? ""
-                  : ",\"IpAddress\":{\"AWS:SourceIp\":\"" + ipAddress + "\"}"
-               )
-               + (activeDate == null
-                  ? ""
-                  : ",\"DateGreaterThan\":{\"AWS:EpochTime\":" + activeDate.getEpochSecond() + "}"
-               )
-               + "}}]}";
+                                           String ipAddress) {
+        Validate.notNull(resourceUrl, "resourceUrl must not be null");
+        Validate.notNull(expirationDate, "expirationDate must not be null");
+        validateInput(resourceUrl, "resourceUrl");
+        if (ipAddress != null) {
+            validateInput(ipAddress, "ipAddress");
+        }
+
+        JsonWriter writer = JsonWriter.create();
+        writer.writeStartObject()
+              .writeFieldName("Statement")
+              .writeStartArray()
+              .writeStartObject()
+              .writeFieldName("Resource")
+              .writeValue(resourceUrl)
+              .writeFieldName("Condition")
+              .writeStartObject()
+              .writeFieldName("DateLessThan")
+              .writeStartObject()
+              .writeFieldName("AWS:EpochTime")
+              .writeValue(expirationDate.getEpochSecond())
+              .writeEndObject();
+
+        if (ipAddress != null) {
+            writer.writeFieldName("IpAddress")
+                  .writeStartObject()
+                  .writeFieldName("AWS:SourceIp")
+                  .writeValue(ipAddress)
+                  .writeEndObject();
+        }
+
+        if (activeDate != null) {
+            writer.writeFieldName("DateGreaterThan")
+                  .writeStartObject()
+                  .writeFieldName("AWS:EpochTime")
+                  .writeValue(activeDate.getEpochSecond())
+                  .writeEndObject();
+        }
+
+        writer.writeEndObject()
+              .writeEndObject()
+              .writeEndArray()
+              .writeEndObject();
+
+        return new String(writer.getBytes(), UTF_8);
+    }
+
+    /**
+     * Validates that the input does not contain characters that could be used for JSON injection attacks.
+     * Double quotes, backslashes, and control characters should never appear in valid CloudFront resource URLs
+     * or IP addresses.
+     *
+     * @param input the input string to validate
+     * @param paramName the parameter name for error messages
+     * @throws IllegalArgumentException if the input contains invalid characters
+     */
+    private static void validateInput(String input, String paramName) {
+        for (int i = 0; i < input.length(); i++) {
+            char c = input.charAt(i);
+            if (c == '"' || c == '\\' || Character.isISOControl(c)) {
+                throw new IllegalArgumentException(
+                    paramName + " contains invalid characters. The character '" + c + "' at position " + i +
+                    " is not allowed. URLs and IP addresses should be properly encoded and must not contain " +
+                    "double quotes, backslashes, or control characters.");
+            }
+        }
     }
 
     /**
diff --git a/services/cloudfront/src/test/java/software/amazon/awssdk/services/cloudfront/CloudFrontUtilitiesTest.java b/services/cloudfront/src/test/java/software/amazon/awssdk/services/cloudfront/CloudFrontUtilitiesTest.java
index a07e26d1e0ce..8e69a92597a2 100644
--- a/services/cloudfront/src/test/java/software/amazon/awssdk/services/cloudfront/CloudFrontUtilitiesTest.java
+++ b/services/cloudfront/src/test/java/software/amazon/awssdk/services/cloudfront/CloudFrontUtilitiesTest.java
@@ -429,7 +429,7 @@ void getSignedURLWithCustomPolicy_policyResourceUrlShouldHandleVariousPatterns(
         StringJoiner conditions = new StringJoiner(",", "{", "}");
         conditions.add("\"DateLessThan\":{\"AWS:EpochTime\":" + expiration.getEpochSecond() + "}");
 
-        expectedPolicy.append("{\"Statement\": [{")
+        expectedPolicy.append("{\"Statement\":[{")
                       .append("\"Resource\":\"").append(expectedResource).append("\",")
                       .append("\"Condition\":").append(conditions)
                       .append("}]}");
diff --git a/services/cloudfront/src/test/java/software/amazon/awssdk/services/cloudfront/internal/utils/SigningUtilsTest.java b/services/cloudfront/src/test/java/software/amazon/awssdk/services/cloudfront/internal/utils/SigningUtilsTest.java
new file mode 100644
index 000000000000..c6c9011a492d
--- /dev/null
+++ b/services/cloudfront/src/test/java/software/amazon/awssdk/services/cloudfront/internal/utils/SigningUtilsTest.java
@@ -0,0 +1,176 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file 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 software.amazon.awssdk.services.cloudfront.internal.utils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import java.time.Instant;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+class SigningUtilsTest {
+
+    private static final Instant EXPIRATION = Instant.ofEpochSecond(1704067200);
+    private static final Instant ACTIVE_DATE = Instant.ofEpochSecond(1640995200);
+    private static final String VALID_URL = "https://d111111abcdef8.cloudfront.net/s3ObjectKey";
+    private static final String VALID_IP = "192.168.1.0/24";
+
+    @Test
+    void buildCannedPolicy_withValidUrl_producesValidJson() {
+        String policy = SigningUtils.buildCannedPolicy(VALID_URL, EXPIRATION);
+
+        assertThat(policy).contains("\"Resource\":\"" + VALID_URL + "\"");
+        assertThat(policy).contains("\"AWS:EpochTime\":" + EXPIRATION.getEpochSecond());
+        // Verify it's valid JSON structure
+        assertThat(policy).startsWith("{");
+        assertThat(policy).endsWith("}");
+    }
+
+    @Test
+    void buildCustomPolicy_withAllParameters_producesValidJson() {
+        String policy = SigningUtils.buildCustomPolicy(VALID_URL, ACTIVE_DATE, EXPIRATION, VALID_IP);
+
+        assertThat(policy).contains("\"Resource\":\"" + VALID_URL + "\"");
+        assertThat(policy).contains("\"DateLessThan\"");
+        assertThat(policy).contains("\"DateGreaterThan\"");
+        assertThat(policy).contains("\"IpAddress\"");
+        assertThat(policy).contains("\"AWS:SourceIp\":\"" + VALID_IP + "\"");
+    }
+
+
+    @Test
+    void buildCannedPolicy_withDoubleQuoteInUrl_shouldRejectInput() {
+        String maliciousUrl = "https://example.com/file\",\"Resource\":\"*\",\"x\":\"";
+
+        assertThatThrownBy(() -> SigningUtils.buildCannedPolicy(maliciousUrl, EXPIRATION))
+            .isInstanceOf(IllegalArgumentException.class)
+            .hasMessageContaining("contains invalid characters")
+            .hasMessageContaining("resourceUrl");
+    }
+
+    @Test
+    void buildCannedPolicy_withBackslashInUrl_shouldRejectInput() {
+        String maliciousUrl = "https://example.com/file\\";
+
+        assertThatThrownBy(() -> SigningUtils.buildCannedPolicy(maliciousUrl, EXPIRATION))
+            .isInstanceOf(IllegalArgumentException.class)
+            .hasMessageContaining("contains invalid characters");
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {
+        "https://example.com/file\u0000",  // null character
+        "https://example.com/file\n",      // newline
+        "https://example.com/file\r",      // carriage return
+        "https://example.com/file\t"       // tab
+    })
+    void buildCannedPolicy_withControlCharactersInUrl_shouldRejectInput(String maliciousUrl) {
+        assertThatThrownBy(() -> SigningUtils.buildCannedPolicy(maliciousUrl, EXPIRATION))
+            .isInstanceOf(IllegalArgumentException.class)
+            .hasMessageContaining("contains invalid characters");
+    }
+
+    @Test
+    void buildCustomPolicy_withDoubleQuoteInUrl_shouldRejectInput() {
+        String maliciousUrl = "https://example.com/file\"";
+
+        assertThatThrownBy(() -> SigningUtils.buildCustomPolicy(maliciousUrl, ACTIVE_DATE, EXPIRATION, VALID_IP))
+            .isInstanceOf(IllegalArgumentException.class)
+            .hasMessageContaining("resourceUrl");
+    }
+
+    @Test
+    void buildCustomPolicy_withDoubleQuoteInIpAddress_shouldRejectInput() {
+        String maliciousIp = "192.168.1.0\",\"Resource\":\"*";
+
+        assertThatThrownBy(() -> SigningUtils.buildCustomPolicy(VALID_URL, ACTIVE_DATE, EXPIRATION, maliciousIp))
+            .isInstanceOf(IllegalArgumentException.class)
+            .hasMessageContaining("ipAddress");
+    }
+
+    @Test
+    void buildCustomPolicyForSignedUrl_withDoubleQuoteInUrl_shouldRejectInput() {
+        String maliciousUrl = "https://example.com/file\"";
+
+        assertThatThrownBy(() -> SigningUtils.buildCustomPolicyForSignedUrl(maliciousUrl, ACTIVE_DATE, EXPIRATION, VALID_IP))
+            .isInstanceOf(IllegalArgumentException.class)
+            .hasMessageContaining("contains invalid characters");
+    }
+
+    @Test
+    void buildCustomPolicyForSignedUrl_withDoubleQuoteInIpRange_shouldRejectInput() {
+        String maliciousIp = "192.168.1.0\"";
+
+        assertThatThrownBy(() -> SigningUtils.buildCustomPolicyForSignedUrl(VALID_URL, ACTIVE_DATE, EXPIRATION, maliciousIp))
+            .isInstanceOf(IllegalArgumentException.class)
+            .hasMessageContaining("contains invalid characters");
+    }
+
+    // Null parameter validation tests
+
+    @Test
+    void buildCannedPolicy_withNullUrl_shouldThrowNullPointerException() {
+        assertThatThrownBy(() -> SigningUtils.buildCannedPolicy(null, EXPIRATION))
+            .isInstanceOf(NullPointerException.class)
+            .hasMessageContaining("resourceUrl");
+    }
+
+    @Test
+    void buildCannedPolicy_withNullExpiration_shouldThrowNullPointerException() {
+        assertThatThrownBy(() -> SigningUtils.buildCannedPolicy(VALID_URL, null))
+            .isInstanceOf(NullPointerException.class)
+            .hasMessageContaining("expirationDate");
+    }
+
+    @Test
+    void buildCustomPolicy_withNullUrl_shouldThrowNullPointerException() {
+        assertThatThrownBy(() -> SigningUtils.buildCustomPolicy(null, ACTIVE_DATE, EXPIRATION, VALID_IP))
+            .isInstanceOf(NullPointerException.class)
+            .hasMessageContaining("resourceUrl");
+    }
+
+    @Test
+    void buildCustomPolicy_withNullExpiration_shouldThrowNullPointerException() {
+        assertThatThrownBy(() -> SigningUtils.buildCustomPolicy(VALID_URL, ACTIVE_DATE, null, VALID_IP))
+            .isInstanceOf(NullPointerException.class)
+            .hasMessageContaining("expirationDate");
+    }
+
+    // Valid edge cases that should still work
+
+    @Test
+    void buildCannedPolicy_withWildcard_shouldSucceed() {
+        String policy = SigningUtils.buildCannedPolicy("*", EXPIRATION);
+        assertThat(policy).contains("\"Resource\":\"*\"");
+    }
+
+    @Test
+    void buildCannedPolicy_withWildcardInPath_shouldSucceed() {
+        String url = "https://d111111abcdef8.cloudfront.net/*";
+        String policy = SigningUtils.buildCannedPolicy(url, EXPIRATION);
+        assertThat(policy).contains("\"Resource\":\"" + url + "\"");
+    }
+
+    @Test
+    void buildCannedPolicy_withQueryParameters_shouldSucceed() {
+        String url = "https://d111111abcdef8.cloudfront.net/file?param=value&other=123";
+        String policy = SigningUtils.buildCannedPolicy(url, EXPIRATION);
+        assertThat(policy).contains("\"Resource\":\"" + url + "\"");
+    }
+
+}