CVE-2026-6011

@@ -41,6 +41,7 @@ Status: unreleased.
 - Security: harden Tailscale Serve auth by validating identity via local tailscaled before trusting headers.
 - Build: align memory-core peer dependency with lockfile.
 - Security: add mDNS discovery mode with minimal default to reduce information disclosure. (#1882) Thanks @orlyjamie.
+- Security: harden URL fetches with DNS pinning to reduce rebinding risk. Thanks Chris Zheng.
 - Web UI: improve WebChat image paste previews and allow image-only sends. (#1925) Thanks @smartprogrammer93.
 - Security: wrap external hook content by default with a per-hook opt-out. (#1827) Thanks @mertcicekci0.
 - Gateway: default auth now fail-closed (token/password required; Tailscale Serve identity remains allowed).

@@ -1,7 +1,13 @@
 import { Type } from "@sinclair/typebox";
 
 import type { ClawdbotConfig } from "../../config/config.js";
-import { assertPublicHostname, SsrFBlockedError } from "../../infra/net/ssrf.js";
+import {
+  closeDispatcher,
+  createPinnedDispatcher,
+  resolvePinnedHostname,
+  SsrFBlockedError,
+} from "../../infra/net/ssrf.js";
+import type { Dispatcher } from "undici";
 import { stringEnum } from "../schema/typebox.js";
 import type { AnyAgentTool } from "./common.js";
 import { jsonResult, readNumberParam, readStringParam } from "./common.js";
@@ -167,7 +173,7 @@ async function fetchWithRedirects(params: {
   maxRedirects: number;
   timeoutSeconds: number;
   userAgent: string;
-}): Promise<{ response: Response; finalUrl: string }> {
+}): Promise<{ response: Response; finalUrl: string; dispatcher: Dispatcher }> {
   const signal = withTimeout(undefined, params.timeoutSeconds * 1000);
   const visited = new Set<string>();
   let currentUrl = params.url;
@@ -184,39 +190,50 @@ async function fetchWithRedirects(params: {
       throw new Error("Invalid URL: must be http or https");
     }
 
-    await assertPublicHostname(parsedUrl.hostname);
-
-    const res = await fetch(parsedUrl.toString(), {
-      method: "GET",
-      headers: {
-        Accept: "*/*",
-        "User-Agent": params.userAgent,
-        "Accept-Language": "en-US,en;q=0.9",
-      },
-      signal,
-      redirect: "manual",
-    });
+    const pinned = await resolvePinnedHostname(parsedUrl.hostname);
+    const dispatcher = createPinnedDispatcher(pinned);
+    let res: Response;
+    try {
+      res = await fetch(parsedUrl.toString(), {
+        method: "GET",
+        headers: {
+          Accept: "*/*",
+          "User-Agent": params.userAgent,
+          "Accept-Language": "en-US,en;q=0.9",
+        },
+        signal,
+        redirect: "manual",
+        dispatcher,
+      } as RequestInit);
+    } catch (err) {
+      await closeDispatcher(dispatcher);
+      throw err;
+    }
 
     if (isRedirectStatus(res.status)) {
       const location = res.headers.get("location");
       if (!location) {
+        await closeDispatcher(dispatcher);
         throw new Error(`Redirect missing location header (${res.status})`);
       }
       redirectCount += 1;
       if (redirectCount > params.maxRedirects) {
+        await closeDispatcher(dispatcher);
         throw new Error(`Too many redirects (limit: ${params.maxRedirects})`);
       }
       const nextUrl = new URL(location, parsedUrl).toString();
       if (visited.has(nextUrl)) {
+        await closeDispatcher(dispatcher);
         throw new Error("Redirect loop detected");
       }
       visited.add(nextUrl);
       void res.body?.cancel();
+      await closeDispatcher(dispatcher);
       currentUrl = nextUrl;
       continue;
     }
 
-    return { response: res, finalUrl: currentUrl };
+    return { response: res, finalUrl: currentUrl, dispatcher };
   }
 }
 
@@ -348,6 +365,7 @@ async function runWebFetch(params: {
 
   const start = Date.now();
   let res: Response;
+  let dispatcher: Dispatcher | null = null;
   let finalUrl = params.url;
   try {
     const result = await fetchWithRedirects({
@@ -358,6 +376,7 @@ async function runWebFetch(params: {
     });
     res = result.response;
     finalUrl = result.finalUrl;
+    dispatcher = result.dispatcher;
   } catch (error) {
     if (error instanceof SsrFBlockedError) {
       throw error;
@@ -396,108 +415,112 @@ async function runWebFetch(params: {
     throw error;
   }
 
-  if (!res.ok) {
-    if (params.firecrawlEnabled && params.firecrawlApiKey) {
-      const firecrawl = await fetchFirecrawlContent({
-        url: params.url,
-        extractMode: params.extractMode,
-        apiKey: params.firecrawlApiKey,
-        baseUrl: params.firecrawlBaseUrl,
-        onlyMainContent: params.firecrawlOnlyMainContent,
-        maxAgeMs: params.firecrawlMaxAgeMs,
-        proxy: params.firecrawlProxy,
-        storeInCache: params.firecrawlStoreInCache,
-        timeoutSeconds: params.firecrawlTimeoutSeconds,
+  try {
+    if (!res.ok) {
+      if (params.firecrawlEnabled && params.firecrawlApiKey) {
+        const firecrawl = await fetchFirecrawlContent({
+          url: params.url,
+          extractMode: params.extractMode,
+          apiKey: params.firecrawlApiKey,
+          baseUrl: params.firecrawlBaseUrl,
+          onlyMainContent: params.firecrawlOnlyMainContent,
+          maxAgeMs: params.firecrawlMaxAgeMs,
+          proxy: params.firecrawlProxy,
+          storeInCache: params.firecrawlStoreInCache,
+          timeoutSeconds: params.firecrawlTimeoutSeconds,
+        });
+        const truncated = truncateText(firecrawl.text, params.maxChars);
+        const payload = {
+          url: params.url,
+          finalUrl: firecrawl.finalUrl || finalUrl,
+          status: firecrawl.status ?? res.status,
+          contentType: "text/markdown",
+          title: firecrawl.title,
+          extractMode: params.extractMode,
+          extractor: "firecrawl",
+          truncated: truncated.truncated,
+          length: truncated.text.length,
+          fetchedAt: new Date().toISOString(),
+          tookMs: Date.now() - start,
+          text: truncated.text,
+          warning: firecrawl.warning,
+        };
+        writeCache(FETCH_CACHE, cacheKey, payload, params.cacheTtlMs);
+        return payload;
+      }
+      const rawDetail = await readResponseText(res);
+      const detail = formatWebFetchErrorDetail({
+        detail: rawDetail,
+        contentType: res.headers.get("content-type"),
+        maxChars: DEFAULT_ERROR_MAX_CHARS,
       });
-      const truncated = truncateText(firecrawl.text, params.maxChars);
-      const payload = {
-        url: params.url,
-        finalUrl: firecrawl.finalUrl || finalUrl,
-        status: firecrawl.status ?? res.status,
-        contentType: "text/markdown",
-        title: firecrawl.title,
-        extractMode: params.extractMode,
-        extractor: "firecrawl",
-        truncated: truncated.truncated,
-        length: truncated.text.length,
-        fetchedAt: new Date().toISOString(),
-        tookMs: Date.now() - start,
-        text: truncated.text,
-        warning: firecrawl.warning,
-      };
-      writeCache(FETCH_CACHE, cacheKey, payload, params.cacheTtlMs);
-      return payload;
+      throw new Error(`Web fetch failed (${res.status}): ${detail || res.statusText}`);
     }
-    const rawDetail = await readResponseText(res);
-    const detail = formatWebFetchErrorDetail({
-      detail: rawDetail,
-      contentType: res.headers.get("content-type"),
-      maxChars: DEFAULT_ERROR_MAX_CHARS,
-    });
-    throw new Error(`Web fetch failed (${res.status}): ${detail || res.statusText}`);
-  }
-
-  const contentType = res.headers.get("content-type") ?? "application/octet-stream";
-  const body = await readResponseText(res);
 
-  let title: string | undefined;
-  let extractor = "raw";
-  let text = body;
-  if (contentType.includes("text/html")) {
-    if (params.readabilityEnabled) {
-      const readable = await extractReadableContent({
-        html: body,
-        url: finalUrl,
-        extractMode: params.extractMode,
-      });
-      if (readable?.text) {
-        text = readable.text;
-        title = readable.title;
-        extractor = "readability";
-      } else {
-        const firecrawl = await tryFirecrawlFallback({ ...params, url: finalUrl });
-        if (firecrawl) {
-          text = firecrawl.text;
-          title = firecrawl.title;
-          extractor = "firecrawl";
+    const contentType = res.headers.get("content-type") ?? "application/octet-stream";
+    const body = await readResponseText(res);
+
+    let title: string | undefined;
+    let extractor = "raw";
+    let text = body;
+    if (contentType.includes("text/html")) {
+      if (params.readabilityEnabled) {
+        const readable = await extractReadableContent({
+          html: body,
+          url: finalUrl,
+          extractMode: params.extractMode,
+        });
+        if (readable?.text) {
+          text = readable.text;
+          title = readable.title;
+          extractor = "readability";
         } else {
-          throw new Error(
-            "Web fetch extraction failed: Readability and Firecrawl returned no content.",
-          );
+          const firecrawl = await tryFirecrawlFallback({ ...params, url: finalUrl });
+          if (firecrawl) {
+            text = firecrawl.text;
+            title = firecrawl.title;
+            extractor = "firecrawl";
+          } else {
+            throw new Error(
+              "Web fetch extraction failed: Readability and Firecrawl returned no content.",
+            );
+          }
         }
+      } else {
+        throw new Error(
+          "Web fetch extraction failed: Readability disabled and Firecrawl unavailable.",
+        );
+      }
+    } else if (contentType.includes("application/json")) {
+      try {
+        text = JSON.stringify(JSON.parse(body), null, 2);
+        extractor = "json";
+      } catch {
+        text = body;
+        extractor = "raw";
       }
-    } else {
-      throw new Error(
-        "Web fetch extraction failed: Readability disabled and Firecrawl unavailable.",
-      );
-    }
-  } else if (contentType.includes("application/json")) {
-    try {
-      text = JSON.stringify(JSON.parse(body), null, 2);
-      extractor = "json";
-    } catch {
-      text = body;
-      extractor = "raw";
     }
-  }
 
-  const truncated = truncateText(text, params.maxChars);
-  const payload = {
-    url: params.url,
-    finalUrl,
-    status: res.status,
-    contentType,
-    title,
-    extractMode: params.extractMode,
-    extractor,
-    truncated: truncated.truncated,
-    length: truncated.text.length,
-    fetchedAt: new Date().toISOString(),
-    tookMs: Date.now() - start,
-    text: truncated.text,
-  };
-  writeCache(FETCH_CACHE, cacheKey, payload, params.cacheTtlMs);
-  return payload;
+    const truncated = truncateText(text, params.maxChars);
+    const payload = {
+      url: params.url,
+      finalUrl,
+      status: res.status,
+      contentType,
+      title,
+      extractMode: params.extractMode,
+      extractor,
+      truncated: truncated.truncated,
+      length: truncated.text.length,
+      fetchedAt: new Date().toISOString(),
+      tookMs: Date.now() - start,
+      text: truncated.text,
+    };
+    writeCache(FETCH_CACHE, cacheKey, payload, params.cacheTtlMs);
+    return payload;
+  } finally {
+    await closeDispatcher(dispatcher);
+  }
 }
 
 async function tryFirecrawlFallback(params: {

@@ -0,0 +1,63 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { createPinnedLookup, resolvePinnedHostname } from "./ssrf.js";
+
+describe("ssrf pinning", () => {
+  it("pins resolved addresses for the target hostname", async () => {
+    const lookup = vi.fn(async () => [
+      { address: "93.184.216.34", family: 4 },
+      { address: "93.184.216.35", family: 4 },
+    ]);
+
+    const pinned = await resolvePinnedHostname("Example.com.", lookup);
+    expect(pinned.hostname).toBe("example.com");
+    expect(pinned.addresses).toEqual(["93.184.216.34", "93.184.216.35"]);
+
+    const first = await new Promise<{ address: string; family?: number }>((resolve, reject) => {
+      pinned.lookup("example.com", (err, address, family) => {
+        if (err) reject(err);
+        else resolve({ address: address as string, family });
+      });
+    });
+    expect(first.address).toBe("93.184.216.34");
+    expect(first.family).toBe(4);
+
+    const all = await new Promise<unknown>((resolve, reject) => {
+      pinned.lookup("example.com", { all: true }, (err, addresses) => {
+        if (err) reject(err);
+        else resolve(addresses);
+      });
+    });
+    expect(Array.isArray(all)).toBe(true);
+    expect((all as Array<{ address: string }>).map((entry) => entry.address)).toEqual(
+      pinned.addresses,
+    );
+  });
+
+  it("rejects private DNS results", async () => {
+    const lookup = vi.fn(async () => [{ address: "10.0.0.8", family: 4 }]);
+    await expect(resolvePinnedHostname("example.com", lookup)).rejects.toThrow(/private|internal/i);
+  });
+
+  it("falls back for non-matching hostnames", async () => {
+    const fallback = vi.fn((host: string, options?: unknown, callback?: unknown) => {
+      const cb = typeof options === "function" ? options : (callback as () => void);
+      (cb as (err: null, address: string, family: number) => void)(null, "1.2.3.4", 4);
+    });
+    const lookup = createPinnedLookup({
+      hostname: "example.com",
+      addresses: ["93.184.216.34"],
+      fallback,
+    });
+
+    const result = await new Promise<{ address: string }>((resolve, reject) => {
+      lookup("other.test", (err, address) => {
+        if (err) reject(err);
+        else resolve({ address: address as string });
+      });
+    });
+
+    expect(fallback).toHaveBeenCalledTimes(1);
+    expect(result.address).toBe("1.2.3.4");
+  });
+});

@@ -1,4 +1,12 @@
 import { lookup as dnsLookup } from "node:dns/promises";
+import { lookup as dnsLookupCb, type LookupAddress } from "node:dns";
+import { Agent, type Dispatcher } from "undici";
+
+type LookupCallback = (
+  err: NodeJS.ErrnoException | null,
+  address: string | LookupAddress[],
+  family?: number,
+) => void;
 
 export class SsrFBlockedError extends Error {
   constructor(message: string) {
@@ -101,10 +109,71 @@ export function isBlockedHostname(hostname: string): boolean {
   );
 }
 
-export async function assertPublicHostname(
+export function createPinnedLookup(params: {
+  hostname: string;
+  addresses: string[];
+  fallback?: typeof dnsLookupCb;
+}): typeof dnsLookupCb {
+  const normalizedHost = normalizeHostname(params.hostname);
+  const fallback = params.fallback ?? dnsLookupCb;
+  const fallbackLookup = fallback as unknown as (
+    hostname: string,
+    callback: LookupCallback,
+  ) => void;
+  const fallbackWithOptions = fallback as unknown as (
+    hostname: string,
+    options: unknown,
+    callback: LookupCallback,
+  ) => void;
+  const records = params.addresses.map((address) => ({
+    address,
+    family: address.includes(":") ? 6 : 4,
+  }));
+  let index = 0;
+
+  return ((host: string, options?: unknown, callback?: unknown) => {
+    const cb: LookupCallback =
+      typeof options === "function" ? (options as LookupCallback) : (callback as LookupCallback);
+    if (!cb) return;
+    const normalized = normalizeHostname(host);
+    if (!normalized || normalized !== normalizedHost) {
+      if (typeof options === "function" || options === undefined) {
+        return fallbackLookup(host, cb);
+      }
+      return fallbackWithOptions(host, options, cb);
+    }
+
+    const opts =
+      typeof options === "object" && options !== null
+        ? (options as { all?: boolean; family?: number })
+        : {};
+    const requestedFamily =
+      typeof options === "number" ? options : typeof opts.family === "number" ? opts.family : 0;
+    const candidates =
+      requestedFamily === 4 || requestedFamily === 6
+        ? records.filter((entry) => entry.family === requestedFamily)
+        : records;
+    const usable = candidates.length > 0 ? candidates : records;
+    if (opts.all) {
+      cb(null, usable as LookupAddress[]);
+      return;
+    }
+    const chosen = usable[index % usable.length];
+    index += 1;
+    cb(null, chosen.address, chosen.family);
+  }) as typeof dnsLookupCb;
+}
+
+export type PinnedHostname = {
+  hostname: string;
+  addresses: string[];
+  lookup: typeof dnsLookupCb;
+};
+
+export async function resolvePinnedHostname(
   hostname: string,
   lookupFn: LookupFn = dnsLookup,
-): Promise<void> {
+): Promise<PinnedHostname> {
   const normalized = normalizeHostname(hostname);
   if (!normalized) {
     throw new Error("Invalid hostname");
@@ -128,4 +197,46 @@ export async function assertPublicHostname(
       throw new SsrFBlockedError("Blocked: resolves to private/internal IP address");
     }
   }
+
+  const addresses = Array.from(new Set(results.map((entry) => entry.address)));
+  if (addresses.length === 0) {
+    throw new Error(`Unable to resolve hostname: ${hostname}`);
+  }
+
+  return {
+    hostname: normalized,
+    addresses,
+    lookup: createPinnedLookup({ hostname: normalized, addresses }),
+  };
+}
+
+export function createPinnedDispatcher(pinned: PinnedHostname): Dispatcher {
+  return new Agent({
+    connect: {
+      lookup: pinned.lookup,
+    },
+  });
+}
+
+export async function closeDispatcher(dispatcher?: Dispatcher | null): Promise<void> {
+  if (!dispatcher) return;
+  const candidate = dispatcher as { close?: () => Promise<void> | void; destroy?: () => void };
+  try {
+    if (typeof candidate.close === "function") {
+      await candidate.close();
+      return;
+    }
+    if (typeof candidate.destroy === "function") {
+      candidate.destroy();
+    }
+  } catch {
+    // ignore dispatcher cleanup errors
+  }
+}
+
+export async function assertPublicHostname(
+  hostname: string,
+  lookupFn: LookupFn = dnsLookup,
+): Promise<void> {
+  await resolvePinnedHostname(hostname, lookupFn);
 }

@@ -1,5 +1,10 @@
 import { logWarn } from "../logger.js";
-import { assertPublicHostname } from "../infra/net/ssrf.js";
+import {
+  closeDispatcher,
+  createPinnedDispatcher,
+  resolvePinnedHostname,
+} from "../infra/net/ssrf.js";
+import type { Dispatcher } from "undici";
 
 type CanvasModule = typeof import("@napi-rs/canvas");
 type PdfJsModule = typeof import("pdfjs-dist/legacy/build/pdf.mjs");
@@ -154,50 +159,57 @@ export async function fetchWithGuard(params: {
       if (!["http:", "https:"].includes(parsedUrl.protocol)) {
         throw new Error(`Invalid URL protocol: ${parsedUrl.protocol}. Only HTTP/HTTPS allowed.`);
       }
-      await assertPublicHostname(parsedUrl.hostname);
-
-      const response = await fetch(parsedUrl, {
-        signal: controller.signal,
-        headers: { "User-Agent": "Clawdbot-Gateway/1.0" },
-        redirect: "manual",
-      });
-
-      if (isRedirectStatus(response.status)) {
-        const location = response.headers.get("location");
-        if (!location) {
-          throw new Error(`Redirect missing location header (${response.status})`);
+      const pinned = await resolvePinnedHostname(parsedUrl.hostname);
+      const dispatcher = createPinnedDispatcher(pinned);
+
+      try {
+        const response = await fetch(parsedUrl, {
+          signal: controller.signal,
+          headers: { "User-Agent": "Clawdbot-Gateway/1.0" },
+          redirect: "manual",
+          dispatcher,
+        } as RequestInit & { dispatcher: Dispatcher });
+
+        if (isRedirectStatus(response.status)) {
+          const location = response.headers.get("location");
+          if (!location) {
+            throw new Error(`Redirect missing location header (${response.status})`);
+          }
+          redirectCount += 1;
+          if (redirectCount > params.maxRedirects) {
+            throw new Error(`Too many redirects (limit: ${params.maxRedirects})`);
+          }
+          void response.body?.cancel();
+          currentUrl = new URL(location, parsedUrl).toString();
+          continue;
         }
-        redirectCount += 1;
-        if (redirectCount > params.maxRedirects) {
-          throw new Error(`Too many redirects (limit: ${params.maxRedirects})`);
+
+        if (!response.ok) {
+          throw new Error(`Failed to fetch: ${response.status} ${response.statusText}`);
         }
-        currentUrl = new URL(location, parsedUrl).toString();
-        continue;
-      }
 
-      if (!response.ok) {
-        throw new Error(`Failed to fetch: ${response.status} ${response.statusText}`);
-      }
+        const contentLength = response.headers.get("content-length");
+        if (contentLength) {
+          const size = parseInt(contentLength, 10);
+          if (size > params.maxBytes) {
+            throw new Error(`Content too large: ${size} bytes (limit: ${params.maxBytes} bytes)`);
+          }
+        }
 
-      const contentLength = response.headers.get("content-length");
-      if (contentLength) {
-        const size = parseInt(contentLength, 10);
-        if (size > params.maxBytes) {
-          throw new Error(`Content too large: ${size} bytes (limit: ${params.maxBytes} bytes)`);
+        const buffer = Buffer.from(await response.arrayBuffer());
+        if (buffer.byteLength > params.maxBytes) {
+          throw new Error(
+            `Content too large: ${buffer.byteLength} bytes (limit: ${params.maxBytes} bytes)`,
+          );
         }
-      }
 
-      const buffer = Buffer.from(await response.arrayBuffer());
-      if (buffer.byteLength > params.maxBytes) {
-        throw new Error(
-          `Content too large: ${buffer.byteLength} bytes (limit: ${params.maxBytes} bytes)`,
-        );
+        const contentType = response.headers.get("content-type") || undefined;
+        const parsed = parseContentType(contentType);
+        const mimeType = parsed.mimeType ?? "application/octet-stream";
+        return { buffer, mimeType, contentType };
+      } finally {
+        await closeDispatcher(dispatcher);
       }
-
-      const contentType = response.headers.get("content-type") || undefined;
-      const parsed = parseContentType(contentType);
-      const mimeType = parsed.mimeType ?? "application/octet-stream";
-      return { buffer, mimeType, contentType };
     }
   } finally {
     clearTimeout(timeoutId);

@@ -18,6 +18,9 @@ vi.doMock("node:os", () => ({
 vi.doMock("node:https", () => ({
   request: (...args: unknown[]) => mockRequest(...args),
 }));
+vi.doMock("node:dns/promises", () => ({
+  lookup: async () => [{ address: "93.184.216.34", family: 4 }],
+}));
 
 const loadStore = async () => await import("./store.js");
 

@@ -1,10 +1,12 @@
 import crypto from "node:crypto";
 import { createWriteStream } from "node:fs";
 import fs from "node:fs/promises";
-import { request } from "node:https";
+import { request as httpRequest } from "node:http";
+import { request as httpsRequest } from "node:https";
 import path from "node:path";
 import { pipeline } from "node:stream/promises";
 import { resolveConfigDir } from "../utils.js";
+import { resolvePinnedHostname } from "../infra/net/ssrf.js";
 import { detectMime, extensionForMime } from "./mime.js";
 
 const resolveMediaDir = () => path.join(resolveConfigDir(), "media");
@@ -88,51 +90,67 @@ async function downloadToFile(
   maxRedirects = 5,
 ): Promise<{ headerMime?: string; sniffBuffer: Buffer; size: number }> {
   return await new Promise((resolve, reject) => {
-    const req = request(url, { headers }, (res) => {
-      // Follow redirects
-      if (res.statusCode && res.statusCode >= 300 && res.statusCode < 400) {
-        const location = res.headers.location;
-        if (!location || maxRedirects <= 0) {
-          reject(new Error(`Redirect loop or missing Location header`));
-          return;
-        }
-        const redirectUrl = new URL(location, url).href;
-        resolve(downloadToFile(redirectUrl, dest, headers, maxRedirects - 1));
-        return;
-      }
-      if (!res.statusCode || res.statusCode >= 400) {
-        reject(new Error(`HTTP ${res.statusCode ?? "?"} downloading media`));
-        return;
-      }
-      let total = 0;
-      const sniffChunks: Buffer[] = [];
-      let sniffLen = 0;
-      const out = createWriteStream(dest);
-      res.on("data", (chunk) => {
-        total += chunk.length;
-        if (sniffLen < 16384) {
-          sniffChunks.push(chunk);
-          sniffLen += chunk.length;
-        }
-        if (total > MAX_BYTES) {
-          req.destroy(new Error("Media exceeds 5MB limit"));
-        }
-      });
-      pipeline(res, out)
-        .then(() => {
-          const sniffBuffer = Buffer.concat(sniffChunks, Math.min(sniffLen, 16384));
-          const rawHeader = res.headers["content-type"];
-          const headerMime = Array.isArray(rawHeader) ? rawHeader[0] : rawHeader;
-          resolve({
-            headerMime,
-            sniffBuffer,
-            size: total,
+    let parsedUrl: URL;
+    try {
+      parsedUrl = new URL(url);
+    } catch {
+      reject(new Error("Invalid URL"));
+      return;
+    }
+    if (!["http:", "https:"].includes(parsedUrl.protocol)) {
+      reject(new Error(`Invalid URL protocol: ${parsedUrl.protocol}. Only HTTP/HTTPS allowed.`));
+      return;
+    }
+    const requestImpl = parsedUrl.protocol === "https:" ? httpsRequest : httpRequest;
+    resolvePinnedHostname(parsedUrl.hostname)
+      .then((pinned) => {
+        const req = requestImpl(parsedUrl, { headers, lookup: pinned.lookup }, (res) => {
+          // Follow redirects
+          if (res.statusCode && res.statusCode >= 300 && res.statusCode < 400) {
+            const location = res.headers.location;
+            if (!location || maxRedirects <= 0) {
+              reject(new Error(`Redirect loop or missing Location header`));
+              return;
+            }
+            const redirectUrl = new URL(location, url).href;
+            resolve(downloadToFile(redirectUrl, dest, headers, maxRedirects - 1));
+            return;
+          }
+          if (!res.statusCode || res.statusCode >= 400) {
+            reject(new Error(`HTTP ${res.statusCode ?? "?"} downloading media`));
+            return;
+          }
+          let total = 0;
+          const sniffChunks: Buffer[] = [];
+          let sniffLen = 0;
+          const out = createWriteStream(dest);
+          res.on("data", (chunk) => {
+            total += chunk.length;
+            if (sniffLen < 16384) {
+              sniffChunks.push(chunk);
+              sniffLen += chunk.length;
+            }
+            if (total > MAX_BYTES) {
+              req.destroy(new Error("Media exceeds 5MB limit"));
+            }
           });
-        })
-        .catch(reject);
-    });
-    req.on("error", reject);
-    req.end();
+          pipeline(res, out)
+            .then(() => {
+              const sniffBuffer = Buffer.concat(sniffChunks, Math.min(sniffLen, 16384));
+              const rawHeader = res.headers["content-type"];
+              const headerMime = Array.isArray(rawHeader) ? rawHeader[0] : rawHeader;
+              resolve({
+                headerMime,
+                sniffBuffer,
+                size: total,
+              });
+            })
+            .catch(reject);
+        });
+        req.on("error", reject);
+        req.end();
+      })
+      .catch(reject);
   });
 }