fix: MCP server accepts malformed IPv6 loopback hosts (#1180)

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>

Author: joelagnel

src/OpenClaw.Shared/Mcp/McpHttpServer.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Globalization;
 using System.IO;
 using System.Net;
 using System.Security.Cryptography;
@@ -762,7 +763,7 @@ private static bool IsAuthorized(string authToken, string? authHeader)
             Encoding.UTF8.GetBytes(authToken));
     }
 
-    private static bool IsHostAllowed(string? host)
+    internal static bool IsHostAllowed(string? host)
     {
         if (string.IsNullOrEmpty(host)) return false;
         var trimmed = host.Trim();
@@ -772,7 +773,17 @@ private static bool IsHostAllowed(string? host)
             var closeBracket = trimmed.IndexOf(']');
             if (closeBracket < 0) return false;
             var v6 = trimmed.Substring(1, closeBracket - 1);
-            return string.Equals(v6, "::1", StringComparison.Ordinal);
+            if (!string.Equals(v6, "::1", StringComparison.Ordinal)) return false;
+
+            var suffix = trimmed.AsSpan(closeBracket + 1);
+            if (suffix.IsEmpty) return true;
+            return suffix.Length > 1
+                && suffix[0] == ':'
+                && ushort.TryParse(
+                    suffix[1..],
+                    NumberStyles.None,
+                    CultureInfo.InvariantCulture,
+                    out _);
         }
         // IPv4 / hostname: strip trailing :port if present.
         var colon = trimmed.LastIndexOf(':');

tests/OpenClaw.Shared.Tests/McpHttpServerTests.cs

@@ -204,6 +204,24 @@ public async Task Post_WithRebindHost_RejectedWithForbidden()
         finally { server.Dispose(); http.Dispose(); }
     }
 
+    [Theory]
+    [InlineData("[::1]")]
+    [InlineData("[::1]:8765")]
+    public void IsHostAllowed_AcceptsBracketedIpv6Loopback(string host)
+    {
+        Assert.True(McpHttpServer.IsHostAllowed(host));
+    }
+
+    [Theory]
+    [InlineData("[::1]evil")]
+    [InlineData("[::1]:")]
+    [InlineData("[::1]:not-a-port")]
+    [InlineData("[::1]:65536")]
+    public void IsHostAllowed_RejectsMalformedBracketedIpv6Loopback(string host)
+    {
+        Assert.False(McpHttpServer.IsHostAllowed(host));
+    }
+
     [Fact]
     public async Task Post_WithLocalhostHost_Accepted()
     {