[FLINK-39022][security] Set security.ssl.algorithms default value to modern cipher suite #27514

davidradl · 2026-02-05T13:47:38Z

is it safe to remove this line. Can we have a locked down setup with a reduced set of algorithms - that this warning could still be valid for?

+1 on this, we should keep this mitigation for users.

Well, the sentences later are touching cipher customization but not telling what are be the visible symptoms. I would say we should add the visible symptoms into the upcoming new paragpraph together.

Ack, adding back the visible warning line.

davidradl · 2026-02-05T13:43:15Z

should be put out a warning if we find an algorithm that we consider insecure; specifically checking for the older algs we used to use?

We just want to make it more secure which will comply with the latest RFC. Not yet understand what insecure cipher you mean here🤔

Does it make sense to you, that If a custom cipher is supplied that does not comply with the latest RFC, then we put out a warning to draw the users attention to something that looks insecure, because it does not comply with the latest RFC ?

Adding such warnig is fair point but I don't understand how do you plan to do that phisically. The latest RFC suggests 4 suites. If the user add stronger/weaker than the suggested then how do you decide from Flink code whether we should give a warning or not? If you can highlight the logic then I would buy that.

gaborgsomogyi · 2026-02-05T14:51:28Z

Same question here

TLSv1.2 is the default for security.ssl.protocol it and TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 is the new default value of security.ssl algorithm, therefore it is safe to remove here.
https://docs.openssl.org/1.0.2/man1/ciphers/#tls-v12-cipher-suites

-Original file line number
+Diff line change
@@ Expand Up / @@ -150,20 +150,16 @@ security.ssl.rest.authentication-enabled: false @@
     ### Cipher suites
-    {{< hint warning >}}
-    The [IETF RFC 7525](https://tools.ietf.org/html/rfc7525) recommends to use a specific set of cipher suites for strong security.
-    Because these cipher suites were not available on many setups out of the box, Flink's default value is set to a slightly
-    weaker but more compatible cipher suite.
-    We recommend that SSL setups update to the stronger cipher suites, if possible, by adding the below entry to the Flink configuration:
+    For strong security, it is crucial to use modern and robust cipher suites. [IETF RFC 9325](https://www.rfc-editor.org/info/rfc9325), which supersedes the older RFC 7525, provides current recommendations for the secure use of TLS.
+    In response to evolving security standards and to ensure compatibility with modern Java versions, Flink has updated its default cipher suites. Recent JDK updates (affecting versions like 11.0.30+, 17.0.18+, etc.) have disabled older `TLS_RSA_*` cipher suites that lack forward secrecy.
-    ```yaml
-    security.ssl.algorithms: TLS_DHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_DHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
-    ```
+    To support these secure-by-default JDK versions and align with best practices, Flink's default value for `security.ssl.algorithms` is now:
-    If these cipher suites are not supported on your setup, you will see that Flink processes will not be able to connect to each other.
+    `TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384`
-    {{< /hint >}}
+    This default provides strong security and wide compatibility. You can customize the cipher suites using the `security.ssl.algorithms` configuration option if your environment has different requirements.
+    If these cipher suites are not supported on your setup, you will see that Flink processes will not be able to connect to each other.
     ### Complete List of SSL Options
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up / @@ -150,20 +150,16 @@ security.ssl.rest.authentication-enabled: false @@
     ### Cipher suites
-    {{< hint warning >}}
-    The [IETF RFC 7525](https://tools.ietf.org/html/rfc7525) recommends to use a specific set of cipher suites for strong security.
-    Because these cipher suites were not available on many setups out of the box, Flink's default value is set to a slightly
-    weaker but more compatible cipher suite.
-    We recommend that SSL setups update to the stronger cipher suites, if possible, by adding the below entry to the Flink configuration:
+    For strong security, it is crucial to use modern and robust cipher suites. [IETF RFC 9325](https://www.rfc-editor.org/info/rfc9325), which supersedes the older RFC 7525, provides current recommendations for the secure use of TLS.
+    In response to evolving security standards and to ensure compatibility with modern Java versions, Flink has updated its default cipher suites. Recent JDK updates (affecting versions like 11.0.30+, 17.0.18+, etc.) have disabled older `TLS_RSA_*` cipher suites that lack forward secrecy.
-    ```yaml
-    security.ssl.algorithms: TLS_DHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_DHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
-    ```
+    To support these secure-by-default JDK versions and align with best practices, Flink's default value for `security.ssl.algorithms` is now:
-    If these cipher suites are not supported on your setup, you will see that Flink processes will not be able to connect to each other.
+    `TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384`
-    {{< /hint >}}
+    This default provides strong security and wide compatibility. You can customize the cipher suites using the `security.ssl.algorithms` configuration option if your environment has different requirements.
+    If these cipher suites are not supported on your setup, you will see that Flink processes will not be able to connect to each other.
     ### Complete List of SSL Options
@@ Expand Down @@

-Original file line number
+Diff line change
@@ -0,0 +1,45 @@
+    ---
+    title: "Release Notes - Flink 2.3"
+    ---
+    <!--
+    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.
+    -->
+    # Release notes - Flink 2.3
+    These release notes discuss important aspects, such as configuration, behavior or dependencies,
+    that changed between Flink 2.2 and Flink 2.3. Please read these notes carefully if you are
+    planning to upgrade your Flink version to 2.3.
+    ### Core
+    #### Set security.ssl.algorithms default value to modern cipher suite
+    ### [FLINK-39022](https://issues.apache.org/jira/browse/FLINK-39022)
+    A JDK update (affecting JDK 11.0.30+, 17.0.18+, 21.0.10+, and 24+) disabled `TLS_RSA_*` cipher suites.
+    This was done to support forward-secrecy (RFC 9325) and comply with the IETF Draft on *Deprecating Obsolete Key Exchange Methods in TLS*.
+    To support these and future JDK versions, the default value for the Flink configuration option `security.ssl.algorithms` has been changed to a modern, widely available cipher suite:
+    `TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384`
+    This default provides strong security and wide compatibility. You can customize the cipher suites using the `security.ssl.algorithms` configuration option if your environment has different requirements.
+    If these cipher suites are not supported on your setup, you will see that Flink processes will not be able to connect to each other.

-Original file line number
+Diff line change
@@ Expand Up / @@ -88,9 +88,9 @@ @@
             </tr>
             <tr>
                 <td><h5>security.ssl.algorithms</h5></td>
-                <td style="word-wrap: break-word;">"TLS_RSA_WITH_AES_128_CBC_SHA"</td>
+                <td style="word-wrap: break-word;">"TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384"</td>
                 <td>String</td>
-                <td>The comma separated list of standard SSL algorithms to be supported. Read more <a href="http://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#ciphersuites">here</a></td>
+                <td>The comma separated list of standard SSL algorithms to be supported. Read more <a href="https://docs.oracle.com/en/java/javase/11/docs/specs/security/standard-names.html#jsse-cipher-suite-names">here</a></td>
             </tr>
             <tr>
                 <td><h5>security.ssl.internal.cert.fingerprint</h5></td>
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up / @@ -10,9 +10,9 @@ @@
         <tbody>
             <tr>
                 <td><h5>security.ssl.algorithms</h5></td>
-                <td style="word-wrap: break-word;">"TLS_RSA_WITH_AES_128_CBC_SHA"</td>
+                <td style="word-wrap: break-word;">"TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384"</td>
                 <td>String</td>
-                <td>The comma separated list of standard SSL algorithms to be supported. Read more <a href="http://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#ciphersuites">here</a></td>
+                <td>The comma separated list of standard SSL algorithms to be supported. Read more <a href="https://docs.oracle.com/en/java/javase/11/docs/specs/security/standard-names.html#jsse-cipher-suite-names">here</a></td>
             </tr>
             <tr>
                 <td><h5>security.ssl.internal.cert.fingerprint</h5></td>
@@ Expand Down @@

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[FLINK-39022][security] Set security.ssl.algorithms default value to modern cipher suite #27514

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davidradl Feb 5, 2026

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gaborgsomogyi Feb 5, 2026

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gaborgsomogyi Feb 5, 2026

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balassai Feb 5, 2026

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davidradl Feb 5, 2026

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gaborgsomogyi Feb 5, 2026

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davidradl Feb 5, 2026

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gaborgsomogyi Feb 5, 2026

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gaborgsomogyi Feb 5, 2026

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balassai Feb 5, 2026 •

edited

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-Original file line number
+Diff line change
@@ Expand Up @@
          * The standard SSL algorithms to be supported.
          *
          * <p>More options here -
-         * http://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#ciphersuites
+         * https://docs.oracle.com/en/java/javase/11/docs/specs/security/standard-names.html#jsse-cipher-suite-names
          */
         @Documentation.Section(Documentation.Sections.SECURITY_SSL)
         public static final ConfigOption<String> SSL_ALGORITHMS =
                 key("security.ssl.algorithms")
                         .stringType()
-                        .defaultValue("TLS_RSA_WITH_AES_128_CBC_SHA")
+                        .defaultValue(
+                                "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384")
                         .withDescription(
                                 Description.builder()
                                         .text(
                                                 "The comma separated list of standard SSL algorithms to be supported. Read more %s",
                                                 link(
-                                                        "http://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#ciphersuites",
+                                                        "https://docs.oracle.com/en/java/javase/11/docs/specs/security/standard-names.html#jsse-cipher-suite-names",
                                                         "here"))
                                         .build());
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up / @@ -58,4 +58,11 @@ void checkEnableRestSSLAuthentication() { @@
             options.set(SecurityOptions.SSL_REST_AUTHENTICATION_ENABLED, true);
             assertThat(SecurityOptions.isRestSSLAuthenticationEnabled(options)).isTrue();
         }
+        @Test
+        void checkDefaultCipherSuite() {
+            assertThat(SecurityOptions.SSL_ALGORITHMS.defaultValue())
+                    .isEqualTo(
+                            "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384");
+        }
     }

-Original file line number
+Diff line change
@@ Expand Up / @@ -523,11 +523,6 @@ public static String getRestCertificateFingerprint( @@
         private static void addSslProviderConfig(Configuration config, String sslProvider) {
             if (sslProvider.equalsIgnoreCase("OPENSSL")) {
                 OpenSsl.ensureAvailability();
-                // Flink's default algorithm set is not available for openSSL - choose a different one:
-                config.set(
-                        SecurityOptions.SSL_ALGORITHMS,
-                        "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384");
             }
             config.set(SecurityOptions.SSL_PROVIDER, sslProvider);
         }
@@ Expand Down @@

[FLINK-39022][security] Set security.ssl.algorithms default value to modern cipher suite #27514

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balassai Feb 5, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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balassai Feb 5, 2026 •

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