8367049: URL.openConnection throws StringIndexOutOfBoundsException in avm mode

src/java.base/share/classes/java/net/HostPortrange.java

@@ -60,6 +60,15 @@ public int hashCode() {
     }
 
     HostPortrange(String scheme, String host) {
+        // Defensive validation first
+        if (host == null || host.isEmpty()) {
+            throw new IllegalArgumentException("empty authority");
+        }
+
+        // A leading ':' means missing host, which is invalid for URLPermission authorities
+        if (host.charAt(0) == ':') {
+            throw new IllegalArgumentException("missing host in authority: " + host);
+        }
         // Parse the host name.  A name has up to three components, the
         // hostname, a port number, or two numbers representing a port
         // range.   "www.example.com:8080-9090" is a valid host name.

src/java.base/share/classes/java/net/URLPermission.java

@@ -527,6 +527,9 @@ static class Authority {
         HostPortrange p;
 
         Authority(String scheme, String authority) {
+            if (authority == null || authority.isEmpty()) {
+                throw new IllegalArgumentException("Invalid URL authority: empty host");
+            }
             int at = authority.indexOf('@');
             if (at == -1) {
                     p = new HostPortrange(scheme, authority);

test/jdk/java/net/URLPermission/EmptyAuthorityTest.java

@@ -0,0 +1,69 @@
+/*
+* Copyright (c) 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
+* under the terms of the GNU General Public License version 2 only, as
+* published by the Free Software Foundation.
+*
+* This code is distributed in the hope that it will be useful, but WITHOUT
+* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+* version 2 for more details (a copy is included in the LICENSE file that
+* accompanied this code).
+*
+* You should have received a copy of the GNU General Public License version
+* 2 along with this work; if not, write to the Free Software Foundation,
+* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+*
+* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+* or visit www.oracle.com if you need additional information or have any
+* questions.
+*/
+
+/*
+* @test
+* @bug 8367049
+* @summary URLPermission must reject empty/missing host authority with IAE (no SIOOBE)
+* @run testng EmptyAuthorityTest
+*/
+
+import java.net.URLPermission;
+import org.testng.Assert;
+import org.testng.annotations.DataProvider;
+import org.testng.annotations.Test;
+
+public class EmptyAuthorityTest {
+
+    @DataProvider(name = "badUrls")
+    public Object[][] badUrls() {
+        return new Object[][]{
+                { "http:///path" }, // empty authority
+                { "https:///x" }, // empty authority
+                { "http://@/x" }, // userinfo + empty host
+                { "http://user@/x" }, // userinfo + empty host
+                { "http://:80/x" }, // port with no host
+                { "http://[]/x" } // empty IPv6 literal
+        };
+    }
+
+    @DataProvider(name = "goodUrls")
+    public Object[][] goodUrls() {
+        return new Object[][]{
+                { "http://example.com/x" },
+                { "http://example.com:80/x" },
+                { "http://[::1]/x" },
+                { "http://[::1]:8080/x" }
+        };
+    }
+
+    @Test(dataProvider = "badUrls")
+    public void rejectsEmptyOrMalformedAuthority(String url) {
+        Assert.expectThrows(IllegalArgumentException.class, () -> new URLPermission(url));
+    }
+
+    @Test(dataProvider = "goodUrls")
+    public void acceptsValidAuthorities(String url) {
+        new URLPermission(url); // should not throw
+    }
+}