Refuse to migrate a database with an unrecognized schema version

server/src/main/java/com/mirth/connect/server/migration/ServerMigrator.java

@@ -380,7 +380,15 @@ private Version getCurrentVersion() throws MigrationException {
             resultSet = statement.executeQuery("SELECT VERSION FROM SCHEMA_INFO");
 
             if (resultSet.next()) {
-                return Version.fromString(resultSet.getString(1));
+                String schemaVersion = resultSet.getString(1);
+                Version version = Version.fromString(schemaVersion);
+
+                // Returning null would run every migrator from V0 against an unknown schema
+                if (version == null) {
+                    throw new MigrationException("Database schema version \"" + schemaVersion + "\" is not recognized by this server (version " + Version.getLatest() + "). The database may have been created by a newer or different release. No migrations were run.");
+                }
+
+                return version;
             }
 
             return null;

server/src/test/java/com/mirth/connect/server/migration/ServerMigratorTest.java

@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: MPL-2.0
+// SPDX-FileCopyrightText: 2026 Tony Germano <tony@germano.name>
+
+package com.mirth.connect.server.migration;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.mirth.connect.client.core.Version;
+import com.mirth.connect.model.util.MigrationException;
+
+/**
+ * Runs {@link ServerMigrator#migrate()} against an embedded Derby database that already has a
+ * schema, so the version recorded in SCHEMA_INFO decides what happens.
+ */
+public class ServerMigratorTest {
+
+    private static final String URL = "jdbc:derby:memory:servermigrator";
+
+    /** Looks like a version from a newer release, which is how an unknown version shows up. */
+    private static final String UNRECOGNIZED_VERSION = "99.0.0";
+
+    private Connection connection;
+
+    @Before
+    public void setUp() throws Exception {
+        Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
+        connection = DriverManager.getConnection(URL + ";create=true");
+
+        // An existing CONFIGURATION table means the schema is installed and must be migrated.
+        execute("CREATE TABLE CONFIGURATION (CATEGORY VARCHAR(255) NOT NULL, NAME VARCHAR(255) NOT NULL, VALUE CLOB)");
+        execute("CREATE TABLE SCHEMA_INFO (VERSION VARCHAR(40))");
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        if (connection != null) {
+            connection.close();
+        }
+        try {
+            DriverManager.getConnection(URL + ";drop=true");
+        } catch (SQLException e) {
+            // Derby always reports dropping an in-memory database as an exception (SQLState 08006).
+        }
+    }
+
+    @Test
+    public void testLatestVersionIsLeftUnchanged() throws Exception {
+        setSchemaVersion(Version.getLatest().getSchemaVersion());
+
+        newMigrator().migrate();
+
+        assertEquals(Version.getLatest().getSchemaVersion(), getOnlySchemaVersion());
+    }
+
+    @Test
+    public void testUnrecognizedVersionIsRejected() throws Exception {
+        assertNull("UNRECOGNIZED_VERSION is now a real version; pick another", Version.fromString(UNRECOGNIZED_VERSION));
+        setSchemaVersion(UNRECOGNIZED_VERSION);
+
+        MigrationException e = assertThrows(MigrationException.class, () -> newMigrator().migrate());
+
+        assertTrue(e.getMessage(), e.getMessage().contains("\"" + UNRECOGNIZED_VERSION + "\""));
+        assertEquals(UNRECOGNIZED_VERSION, getOnlySchemaVersion());
+    }
+
+    private ServerMigrator newMigrator() {
+        ServerMigrator migrator = new ServerMigrator();
+        migrator.setConnection(connection);
+        migrator.setDatabaseType("derby");
+        return migrator;
+    }
+
+    private void setSchemaVersion(String version) throws SQLException {
+        execute("INSERT INTO SCHEMA_INFO (VERSION) VALUES ('" + version + "')");
+    }
+
+    /** Fails if SCHEMA_INFO does not hold exactly one row. */
+    private String getOnlySchemaVersion() throws SQLException {
+        try (Statement statement = connection.createStatement(); ResultSet resultSet = statement.executeQuery("SELECT VERSION FROM SCHEMA_INFO")) {
+            assertTrue("SCHEMA_INFO is empty", resultSet.next());
+            String version = resultSet.getString(1);
+            assertFalse("SCHEMA_INFO has more than one row", resultSet.next());
+            return version;
+        }
+    }
+
+    private void execute(String sql) throws SQLException {
+        try (Statement statement = connection.createStatement()) {
+            statement.execute(sql);
+        }
+    }
+}