Description

Axios: HTTP adapter streamed responses bypass maxContentLength

Summary

When responseType: 'stream' is used, Axios returns the response stream without enforcing maxContentLength. This bypasses configured response-size limits and allows unbounded downstream consumption.

Details

In lib/adapters/http.js:

786-789: for responseType === 'stream', Axios immediately settles with the stream.

797-810: maxContentLength enforcement exists only in the non-stream buffering branch.

So callers may set maxContentLength and still receive/read arbitrarily large streamed responses.

PoC

Environment:

Axios main at commit f7a4ee2

Node v24.2.0

Steps:

Start an HTTP server that returns a 2 MiB response body.

Call Axios with:

adapter: 'http'

responseType: 'stream'

maxContentLength: 1024

Read the returned stream fully.

Observed:

Success; full 2097152 bytes readable.

Control check:

Same endpoint with responseType: 'text' and same maxContentLength: rejected with maxContentLength size of 1024 exceeded.

Impact

Type: DoS / unbounded response processing. Impacted: Node.js applications relying on maxContentLength as a safety boundary while using streamed Axios responses.

Mitigation

Aliases

References