diff --git a/localstack-core/localstack/services/opensearch/cluster.py b/localstack-core/localstack/services/opensearch/cluster.py
index 65ef2dd9c4ed5..cae1916c90b09 100644
--- a/localstack-core/localstack/services/opensearch/cluster.py
+++ b/localstack-core/localstack/services/opensearch/cluster.py
@@ -675,14 +675,25 @@ def _base_settings(self, dirs) -> CommandSettings:
         settings = {
             "http.port": self.port,
             "http.publish_port": self.port,
-            "transport.port": "0",
             "network.host": self.host,
             "http.compression": "false",
             "path.data": f'"{dirs.data}"',
             "path.repo": f'"{dirs.backup}"',
-            "discovery.type": "single-node",
         }
 
+        # This config option was renamed between 6.7 and 6.8, yet not documented as a breaking change
+        # See https://github.com/elastic/elasticsearch/blob/f220abaf/build-tools/src/main/java/org/elasticsearch/gradle/testclusters/ElasticsearchNode.java#L1349-L1353
+        if self.version.startswith("Elasticsearch_5.") or (
+            self.version.startswith("Elasticsearch_6.") and self.version != "Elasticsearch_6.8"
+        ):
+            settings["transport.tcp.port"] = "0"
+        else:
+            settings["transport.port"] = "0"
+
+        # `discovery.type` had a different meaning in 5.x
+        if not self.version.startswith("Elasticsearch_5."):
+            settings["discovery.type"] = "single-node"
+
         if os.path.exists(os.path.join(dirs.mods, "x-pack-ml")):
             settings["xpack.ml.enabled"] = "false"
 
@@ -690,7 +701,7 @@ def _base_settings(self, dirs) -> CommandSettings:
 
     def _create_env_vars(self, directories: Directories) -> Dict:
         return {
-            "JAVA_HOME": os.path.join(directories.install, "jdk"),
+            **elasticsearch_package.get_installer(self.version).get_java_env_vars(),
             "ES_JAVA_OPTS": os.environ.get("ES_JAVA_OPTS", "-Xms200m -Xmx600m"),
             "ES_TMPDIR": directories.tmp,
         }
diff --git a/localstack-core/localstack/services/opensearch/packages.py b/localstack-core/localstack/services/opensearch/packages.py
index 4610420f330ee..35a7fd933ea91 100644
--- a/localstack-core/localstack/services/opensearch/packages.py
+++ b/localstack-core/localstack/services/opensearch/packages.py
@@ -18,6 +18,7 @@
     OPENSEARCH_PLUGIN_LIST,
 )
 from localstack.packages import InstallTarget, Package, PackageInstaller
+from localstack.packages.java import java_package
 from localstack.services.opensearch import versions
 from localstack.utils.archives import download_and_extract_with_retry
 from localstack.utils.files import chmod_r, load_file, mkdir, rm_rf, save_file
@@ -42,6 +43,8 @@ def __init__(self, default_version: str = OPENSEARCH_DEFAULT_VERSION):
 
     def _get_installer(self, version: str) -> PackageInstaller:
         if version in versions._prefixed_elasticsearch_install_versions:
+            if version.startswith("Elasticsearch_5.") or version.startswith("Elasticsearch_6."):
+                return ElasticsearchLegacyPackageInstaller(version)
             return ElasticsearchPackageInstaller(version)
         else:
             return OpensearchPackageInstaller(version)
@@ -233,6 +236,12 @@ class ElasticsearchPackageInstaller(PackageInstaller):
     def __init__(self, version: str):
         super().__init__("elasticsearch", version)
 
+    def get_java_env_vars(self) -> dict[str, str]:
+        install_dir = self.get_installed_dir()
+        return {
+            "JAVA_HOME": os.path.join(install_dir, "jdk"),
+        }
+
     def _install(self, target: InstallTarget):
         # locally import to avoid having a dependency on ASF when starting the CLI
         from localstack.aws.api.opensearch import EngineType
@@ -263,7 +272,7 @@ def _install(self, target: InstallTarget):
                 **java_system_properties_proxy(),
                 **java_system_properties_ssl(
                     os.path.join(install_dir, "jdk", "bin", "keytool"),
-                    {"JAVA_HOME": os.path.join(install_dir, "jdk")},
+                    self.get_java_env_vars(),
                 ),
             }
             java_opts = system_properties_to_cli_args(sys_props)
@@ -336,5 +345,27 @@ def get_elasticsearch_install_version(self) -> str:
         return versions.get_install_version(self.version)
 
 
+class ElasticsearchLegacyPackageInstaller(ElasticsearchPackageInstaller):
+    """
+    Specialised package installer for ElasticSearch 5.x and 6.x
+
+    It installs Java during setup because these releases of ES do not have a bundled JDK.
+    This should be removed after these versions are dropped in line with AWS EOL, scheduled for Nov 2026.
+    https://docs.aws.amazon.com/opensearch-service/latest/developerguide/what-is.html#choosing-version
+    """
+
+    # ES 5.x and 6.x require Java 8
+    # See: https://www.elastic.co/guide/en/elasticsearch/reference/6.0/zip-targz.html
+    JAVA_VERSION = "8"
+
+    def _prepare_installation(self, target: InstallTarget) -> None:
+        java_package.get_installer(self.JAVA_VERSION).install(target)
+
+    def get_java_env_vars(self) -> dict[str, str]:
+        return {
+            "JAVA_HOME": java_package.get_installer(self.JAVA_VERSION).get_java_home(),
+        }
+
+
 opensearch_package = OpensearchPackage(default_version=OPENSEARCH_DEFAULT_VERSION)
 elasticsearch_package = OpensearchPackage(default_version=ELASTICSEARCH_DEFAULT_VERSION)