CVE-2026-42034: Axios: HTTP adapter streamed uploads bypass maxBodyLength when maxRedirects: 0
### 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: 1. Start an HTTP server that counts uploaded bytes and returns {received}. 2. 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.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-42034?
CVE-2026-42034 is considered a high severity vulnerability due to the potential for oversize data uploads.
How do I fix CVE-2026-42034?
To fix CVE-2026-42034, update Axios to version 1.15.1 or later, or 0.31.1 or later.
What is the impact of CVE-2026-42034?
The impact of CVE-2026-42034 is that it allows for bypassing the maxBodyLength limitation on streamed uploads when maxRedirects is set to 0.
Which versions of Axios are affected by CVE-2026-42034?
Versions of Axios prior to 1.15.1 and 0.31.1 are affected by CVE-2026-42034.
How can I mitigate the risks associated with CVE-2026-42034?
Mitigation of CVE-2026-42034 can be achieved by implementing input validation on upload sizes until an update can be applied.