fix: fetch adaptor is not enforcing max body or content length (#10795)

lib/adapters/fetch.js

@@ -11,6 +11,7 @@ import {
 } from '../helpers/progressEventReducer.js';
 import resolveConfig from '../helpers/resolveConfig.js';
 import settle from '../core/settle.js';
+import estimateDataURLDecodedBytes from '../helpers/estimateDataURLDecodedBytes.js';
 
 const DEFAULT_CHUNK_SIZE = 64 * 1024;
 
@@ -163,8 +164,13 @@ const factory = (env) => {
       headers,
       withCredentials = 'same-origin',
       fetchOptions,
+      maxContentLength,
+      maxBodyLength,
     } = resolveConfig(config);
 
+    const hasMaxContentLength = utils.isNumber(maxContentLength) && maxContentLength > -1;
+    const hasMaxBodyLength = utils.isNumber(maxBodyLength) && maxBodyLength > -1;
+
     let _fetch = envFetch || fetch;
 
     responseType = responseType ? (responseType + '').toLowerCase() : 'text';
@@ -186,6 +192,41 @@ const factory = (env) => {
     let requestContentLength;
 
     try {
+      // Enforce maxContentLength for data: URLs up-front so we never materialize
+      // an oversized payload. The HTTP adapter applies the same check (see http.js
+      // "if (protocol === 'data:')" branch).
+      if (hasMaxContentLength && typeof url === 'string' && url.startsWith('data:')) {
+        const estimated = estimateDataURLDecodedBytes(url);
+        if (estimated > maxContentLength) {
+          throw new AxiosError(
+            'maxContentLength size of ' + maxContentLength + ' exceeded',
+            AxiosError.ERR_BAD_RESPONSE,
+            config,
+            request
+          );
+        }
+      }
+
+      // Enforce maxBodyLength against the outbound request body before dispatch.
+      // Mirrors http.js behavior (ERR_BAD_REQUEST / 'Request body larger than
+      // maxBodyLength limit'). Skip when the body length cannot be determined
+      // (e.g. a live ReadableStream supplied by the caller).
+      if (hasMaxBodyLength && method !== 'get' && method !== 'head') {
+        const outboundLength = await resolveBodyLength(headers, data);
+        if (
+          typeof outboundLength === 'number' &&
+          isFinite(outboundLength) &&
+          outboundLength > maxBodyLength
+        ) {
+          throw new AxiosError(
+            'Request body larger than maxBodyLength limit',
+            AxiosError.ERR_BAD_REQUEST,
+            config,
+            request
+          );
+        }
+      }
+
       if (
         onUploadProgress &&
         supportsRequestStream &&
@@ -252,10 +293,27 @@ const factory = (env) => {
         ? _fetch(request, fetchOptions)
         : _fetch(url, resolvedOptions));
 
+      // Cheap pre-check: if the server honestly declares a content-length that
+      // already exceeds the cap, reject before we start streaming.
+      if (hasMaxContentLength) {
+        const declaredLength = utils.toFiniteNumber(response.headers.get('content-length'));
+        if (declaredLength != null && declaredLength > maxContentLength) {
+          throw new AxiosError(
+            'maxContentLength size of ' + maxContentLength + ' exceeded',
+            AxiosError.ERR_BAD_RESPONSE,
+            config,
+            request
+          );
+        }
+      }
+
       const isStreamResponse =
         supportsResponseStream && (responseType === 'stream' || responseType === 'response');
 
-      if (supportsResponseStream && (onDownloadProgress || (isStreamResponse && unsubscribe))) {
+      if (
+        supportsResponseStream &&
+        (onDownloadProgress || hasMaxContentLength || (isStreamResponse && unsubscribe))
+      ) {
         const options = {};
 
         ['status', 'statusText', 'headers'].forEach((prop) => {
@@ -272,8 +330,24 @@ const factory = (env) => {
             )) ||
           [];
 
+        let bytesRead = 0;
+        const onChunkProgress = (loadedBytes) => {
+          if (hasMaxContentLength) {
+            bytesRead = loadedBytes;
+            if (bytesRead > maxContentLength) {
+              throw new AxiosError(
+                'maxContentLength size of ' + maxContentLength + ' exceeded',
+                AxiosError.ERR_BAD_RESPONSE,
+                config,
+                request
+              );
+            }
+          }
+          onProgress && onProgress(loadedBytes);
+        };
+
         response = new Response(
-          trackStream(response.body, DEFAULT_CHUNK_SIZE, onProgress, () => {
+          trackStream(response.body, DEFAULT_CHUNK_SIZE, onChunkProgress, () => {
             flush && flush();
             unsubscribe && unsubscribe();
           }),
@@ -288,6 +362,33 @@ const factory = (env) => {
         config
       );
 
+      // Fallback enforcement for environments without ReadableStream support
+      // (legacy runtimes). Detect materialized size from typed output; skip
+      // streams/Response passthrough since the user will read those themselves.
+      if (hasMaxContentLength && !supportsResponseStream && !isStreamResponse) {
+        let materializedSize;
+        if (responseData != null) {
+          if (typeof responseData.byteLength === 'number') {
+            materializedSize = responseData.byteLength;
+          } else if (typeof responseData.size === 'number') {
+            materializedSize = responseData.size;
+          } else if (typeof responseData === 'string') {
+            materializedSize =
+              typeof TextEncoder === 'function'
+                ? new TextEncoder().encode(responseData).byteLength
+                : responseData.length;
+          }
+        }
+        if (typeof materializedSize === 'number' && materializedSize > maxContentLength) {
+          throw new AxiosError(
+            'maxContentLength size of ' + maxContentLength + ' exceeded',
+            AxiosError.ERR_BAD_RESPONSE,
+            config,
+            request
+          );
+        }
+      }
+
       !isStreamResponse && unsubscribe && unsubscribe();
 
       return await new Promise((resolve, reject) => {

lib/helpers/estimateDataURLDecodedBytes.js

@@ -69,5 +69,16 @@ export default function estimateDataURLDecodedBytes(url) {
     return bytes > 0 ? bytes : 0;
   }
 
-  return Buffer.byteLength(body, 'utf8');
+  if (typeof Buffer !== 'undefined' && typeof Buffer.byteLength === 'function') {
+    return Buffer.byteLength(body, 'utf8');
+  }
+
+  // Browser/worker fallback: use TextEncoder when available, else fall back to
+  // raw string length as an upper-bound heuristic. Both are safe for a DoS
+  // guard (over-counting only makes the check stricter for non-ASCII content).
+  if (typeof TextEncoder === 'function') {
+    return new TextEncoder().encode(body).byteLength;
+  }
+
+  return body.length;
 }

tests/unit/adapters/fetch.test.js

@@ -732,6 +732,171 @@ describe.runIf(typeof fetch === 'function')('supports fetch with nodejs', () =>
     });
   });
 
+  describe('size limits (GHSA-777c-7fjr-54vf)', () => {
+    it('should reject an outbound body that exceeds maxBodyLength with ERR_BAD_REQUEST', async () => {
+      const server = await startHTTPServer(
+        (req, res) => {
+          res.end('ok');
+        },
+        { port: SERVER_PORT }
+      );
+
+      try {
+        await assert.rejects(
+          fetchAxios.post(`${LOCAL_SERVER_URL}/`, 'A'.repeat(2048), {
+            maxBodyLength: 1024,
+          }),
+          (err) => {
+            assert.strictEqual(err.code, 'ERR_BAD_REQUEST');
+            assert.match(err.message, /Request body larger than maxBodyLength limit/);
+            return true;
+          }
+        );
+      } finally {
+        await stopHTTPServer(server);
+      }
+    });
+
+    it('should reject a response whose Content-Length exceeds maxContentLength with ERR_BAD_RESPONSE', async () => {
+      const payload = 'A'.repeat(8 * 1024);
+      const server = await startHTTPServer(
+        (req, res) => {
+          res.setHeader('Content-Length', Buffer.byteLength(payload));
+          res.end(payload);
+        },
+        { port: SERVER_PORT }
+      );
+
+      try {
+        await assert.rejects(
+          fetchAxios.get(`${LOCAL_SERVER_URL}/`, {
+            maxContentLength: 1024,
+          }),
+          (err) => {
+            assert.strictEqual(err.code, 'ERR_BAD_RESPONSE');
+            assert.match(err.message, /maxContentLength size of 1024 exceeded/);
+            return true;
+          }
+        );
+      } finally {
+        await stopHTTPServer(server);
+      }
+    });
+
+    it('should reject a chunked response that exceeds maxContentLength during streaming', async () => {
+      const server = await startHTTPServer(
+        (req, res) => {
+          // Omit content-length so the cheap pre-check cannot fire; force
+          // the stream-based enforcement path.
+          res.setHeader('Transfer-Encoding', 'chunked');
+          const chunk = 'B'.repeat(1024);
+          let sent = 0;
+          const writeNext = () => {
+            if (sent >= 8) {
+              return res.end();
+            }
+            sent++;
+            res.write(chunk, writeNext);
+          };
+          writeNext();
+        },
+        { port: SERVER_PORT }
+      );
+
+      try {
+        await assert.rejects(
+          fetchAxios.get(`${LOCAL_SERVER_URL}/`, {
+            maxContentLength: 512,
+          }),
+          (err) => {
+            assert.strictEqual(err.code, 'ERR_BAD_RESPONSE');
+            assert.match(err.message, /maxContentLength size of 512 exceeded/);
+            return true;
+          }
+        );
+      } finally {
+        await stopHTTPServer(server);
+      }
+    });
+
+    it('should reject a data: URL whose decoded size exceeds maxContentLength (base64)', async () => {
+      const payload = 'A'.repeat(4096);
+      const dataUrl = 'data:application/octet-stream;base64,' + Buffer.from(payload).toString('base64');
+
+      // Use a dedicated instance without baseURL — combineURLs would otherwise
+      // prepend baseURL to a data: URL and neutralise the pre-check.
+      const bareAxios = axios.create({ adapter: 'fetch' });
+
+      await assert.rejects(
+        bareAxios.get(dataUrl, { maxContentLength: 16 }),
+        (err) => {
+          assert.strictEqual(err.code, 'ERR_BAD_RESPONSE');
+          assert.match(err.message, /maxContentLength size of 16 exceeded/);
+          return true;
+        }
+      );
+    });
+
+    it('should reject a data: URL whose body size exceeds maxContentLength (non-base64)', async () => {
+      const dataUrl = 'data:text/plain,' + 'X'.repeat(4096);
+
+      const bareAxios = axios.create({ adapter: 'fetch' });
+
+      await assert.rejects(
+        bareAxios.get(dataUrl, { maxContentLength: 16 }),
+        (err) => {
+          assert.strictEqual(err.code, 'ERR_BAD_RESPONSE');
+          assert.match(err.message, /maxContentLength size of 16 exceeded/);
+          return true;
+        }
+      );
+    });
+
+    it('should allow a response at or below maxContentLength', async () => {
+      const payload = 'ok';
+      const server = await startHTTPServer(
+        (req, res) => {
+          res.end(payload);
+        },
+        { port: SERVER_PORT }
+      );
+
+      try {
+        const { data } = await fetchAxios.get(`${LOCAL_SERVER_URL}/`, {
+          maxContentLength: 1024,
+        });
+        assert.strictEqual(data, payload);
+      } finally {
+        await stopHTTPServer(server);
+      }
+    });
+
+    it('should allow a body at or below maxBodyLength', async () => {
+      const payload = 'hello';
+      let received;
+      const server = await startHTTPServer(
+        (req, res) => {
+          const chunks = [];
+          req.on('data', (c) => chunks.push(c));
+          req.on('end', () => {
+            received = Buffer.concat(chunks).toString();
+            res.end('ok');
+          });
+        },
+        { port: SERVER_PORT }
+      );
+
+      try {
+        await fetchAxios.post(`${LOCAL_SERVER_URL}/`, payload, {
+          maxBodyLength: 1024,
+        });
+        assert.strictEqual(received, payload);
+      } finally {
+        await stopHTTPServer(server);
+      }
+    });
+  });
+
   describe('capability probe cleanup', () => {
     it('should cancel the ReadableStream created during the request stream probe', () => {
       // The fetch adapter factory probes for request-stream support by creating