diff --git a/main.py b/main.py
index e6aabc57..98778559 100644
--- a/main.py
+++ b/main.py
@@ -23,6 +23,7 @@
 import concurrent.futures
 import threading
 import ipaddress
+import socket
 from urllib.parse import urlparse
 from typing import Dict, List, Optional, Any, Set, Sequence
 
@@ -209,8 +210,21 @@ def validate_folder_url(url: str) -> bool:
                 log.warning(f"Skipping unsafe URL (private IP): {sanitize_for_log(url)}")
                 return False
         except ValueError:
-            # Not an IP literal, it's a domain.
-            pass
+            # Not an IP literal, it's a domain. Resolve it to prevent SSRF against internal services.
+            try:
+                # Use getaddrinfo to support both IPv4 and IPv6 and check all resolved addresses
+                addr_info = socket.getaddrinfo(hostname, None)
+                for res in addr_info:
+                    # res is (family, type, proto, canonname, sockaddr)
+                    # sockaddr is (address, port) for IPv4 and (address, port, flow info, scope id) for IPv6
+                    ip_str = res[4][0]
+                    ip_obj = ipaddress.ip_address(ip_str)
+                    if ip_obj.is_private or ip_obj.is_loopback:
+                        log.warning(f"Skipping unsafe URL (domain resolves to private IP {ip_str}): {sanitize_for_log(url)}")
+                        return False
+            except Exception as e:
+                log.warning(f"Skipping unsafe URL (DNS resolution failed): {sanitize_for_log(url)} ({e})")
+                return False
 
     except Exception as e:
         log.warning(f"Failed to validate URL {sanitize_for_log(url)}: {e}")
diff --git a/tests/test_ssrf.py b/tests/test_ssrf.py
new file mode 100644
index 00000000..e67d4d58
--- /dev/null
+++ b/tests/test_ssrf.py
@@ -0,0 +1,70 @@
+import unittest
+from unittest.mock import patch
+import sys
+import os
+import socket
+
+# Add parent directory to path to import main
+sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from main import validate_folder_url
+
+class TestSSRF(unittest.TestCase):
+    def test_localhost_literal(self):
+        """Test that explicit localhost strings are rejected."""
+        self.assertFalse(validate_folder_url("https://localhost/config.json"))
+        self.assertFalse(validate_folder_url("https://127.0.0.1/config.json"))
+        self.assertFalse(validate_folder_url("https://[::1]/config.json"))
+
+    @patch('socket.getaddrinfo')
+    def test_private_ipv4_resolution(self, mock_getaddrinfo):
+        """Test that domains resolving to private IPv4 are rejected."""
+        # mock returns list of (family, type, proto, canonname, sockaddr)
+        mock_getaddrinfo.return_value = [
+            (socket.AF_INET, socket.SOCK_STREAM, 6, '', ('192.168.1.1', 0))
+        ]
+        url = "https://internal.private/config.json"
+
+        self.assertFalse(validate_folder_url(url), "Should reject domain resolving to private IPv4")
+
+    @patch('socket.getaddrinfo')
+    def test_private_ipv6_resolution(self, mock_getaddrinfo):
+        """Test that domains resolving to private IPv6 are rejected."""
+        mock_getaddrinfo.return_value = [
+            (socket.AF_INET6, socket.SOCK_STREAM, 6, '', ('fd00::1', 0, 0, 0))
+        ]
+        url = "https://internal6.private/config.json"
+
+        self.assertFalse(validate_folder_url(url), "Should reject domain resolving to private IPv6")
+
+    @patch('socket.getaddrinfo')
+    def test_mixed_resolution_unsafe(self, mock_getaddrinfo):
+        """Test that if ANY resolved IP is private, it is rejected."""
+        mock_getaddrinfo.return_value = [
+            (socket.AF_INET, socket.SOCK_STREAM, 6, '', ('8.8.8.8', 0)),
+            (socket.AF_INET, socket.SOCK_STREAM, 6, '', ('192.168.1.1', 0))
+        ]
+        url = "https://mixed.private/config.json"
+
+        self.assertFalse(validate_folder_url(url), "Should reject if any IP is private")
+
+    @patch('socket.getaddrinfo')
+    def test_public_resolution(self, mock_getaddrinfo):
+        """Test that domains resolving to only public IPs are accepted."""
+        mock_getaddrinfo.return_value = [
+            (socket.AF_INET, socket.SOCK_STREAM, 6, '', ('8.8.8.8', 0))
+        ]
+        url = "https://google.com/config.json"
+
+        self.assertTrue(validate_folder_url(url), "Should accept domain resolving to public IP")
+
+    @patch('socket.getaddrinfo')
+    def test_dns_resolution_failure(self, mock_getaddrinfo):
+        """Test that domains failing resolution are rejected."""
+        mock_getaddrinfo.side_effect = Exception("DNS lookup failed")
+        url = "https://nonexistent.domain/config.json"
+
+        self.assertFalse(validate_folder_url(url), "Should reject domain that fails resolution")
+
+if __name__ == '__main__':
+    unittest.main()