Overview
About vulnerability
Summary
For stream request bodies, maxBodyLength is bypassed when maxRedirects is set to 0 (native http/https transport path). Oversized streamed uploads are sent fully even when the caller sets strict body limits.
Details
Relevant flow in lib/adapters/http.js:
- 556-564: maxBodyLength check applies only to buffered/non-stream data.
- 681-682: maxRedirects === 0 selects native http/https transport.
- 694-699: options.maxBodyLength is set, but native transport does not enforce it.
- 925-945: stream is piped directly to socket (data.pipe(req)) with no Axios byte counting.
This creates a path-specific bypass for streamed uploads.
PoC
Environment:
- Axios main at commit f7a4ee2
- Node v24.2.0
Steps:
- Start an HTTP server that counts uploaded bytes and returns {received}.
- Send a 2 MiB Readable stream with:
- adapter: ‘http’
- maxBodyLength: 1024
- maxRedirects: 0
Observed:
- Request succeeds; server reports received: 2097152.
Control checks:
- Same stream with default/nonzero redirects: rejected with ERR_FR_MAX_BODY_LENGTH_EXCEEDED.
- Buffered body with maxRedirects: 0: rejected with ERR_BAD_REQUEST.
Impact
Type: DoS / uncontrolled upstream upload / resource exhaustion. Impacted: Node.js services using streamed request bodies with maxBodyLength expecting hard enforcement, especially when following Axios guidance to use maxRedirects: 0 for streams.
Details
- Affected product:
- axios , browser-sync , localtunnel , nguniversal
- Affected packages:
- axios @ 1.6.8 (+14 more)