CVE-2026-42034

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.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2026-42034 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.15.1, 0.31.1); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-42034? CVE-2026-42034 is a medium-severity allocation of resources without limits or throttling vulnerability in axios (npm), affecting versions >= 1.0.0, < 1.15.1. It is fixed in 1.15.1, 0.31.1. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is CVE-2026-42034? CVE-2026-42034 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of axios are affected by CVE-2026-42034? axios (npm) versions >= 1.0.0, < 1.15.1 is affected.
4. Is there a fix for CVE-2026-42034? Yes. CVE-2026-42034 is fixed in 1.15.1, 0.31.1. Upgrade to this version or later.
5. Is CVE-2026-42034 exploitable, and should I be worried? Whether CVE-2026-42034 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-42034 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-42034?
   • Upgrade axios to 1.15.1 or later
   • Upgrade axios to 0.31.1 or later