# CVE-2026-101899: Axios NO_PROXY CIDR notation bypass in Node.js adapter

Source: https://junglewise.ai/threats/cve-2026-101899-axios-cidr-form-no-proxy-entries-are-ignored-causing-proxy  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-09-30  
License: CC BY 4.0 with a link back

CVE-2026-101899 · Severity: medium · CVSS 4 · Published 2026-10-13

Axios, a popular HTTP client library for JavaScript, fails to recognize CIDR notation (like 127.0.0.0/8) in NO_PROXY environment variables, causing requests to internal IP ranges to be sent through proxies when they should be excluded. In cloud, container, and enterprise environments that use proxy configurations with CIDR-based exclusion lists, this can expose sensitive request metadata, URLs, headers, and credentials to untrusted proxies.

Technologies: [Axios](https://junglewise.ai/threats/technologies/axios), [axios (npm)](https://junglewise.ai/threats/technologies/npm-axios). Vendors: [Axios](https://junglewise.ai/threats/vendors/axios), [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-101899 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-101899 being exploited in the wild.

**How severe is CVE-2026-101899?** Medium severity, with a CVSS score of 4, published 13 October 2026.

**Which products and versions are affected?** Axios 1.17.0 through 1.18.1; axios (npm) >= 1.15.0, < 1.20.0, SEMVER:introduced=1.15.0,fixed=1.20.0.

**Is there a fix for CVE-2026-101899?** Yes. axios (npm): upgrade to 1.20.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-101899 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-101899?** Check whether you run Axios or axios (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- axios (npm): upgrade to 1.20.0 or later

  ```sh
  npm install axios@1.20.0
  ```


## Technical details

The Node.js adapter's shouldBypassProxy function parses NO_PROXY entries but does not support CIDR notation, treating entries like "127.0.0.0/8" as literal hostnames rather than network ranges. This causes requests to IPs that fall within excluded CIDR blocks to bypass the exclusion policy and route through the proxy. Exact hostname and IP exclusions continue to work; only CIDR-form entries fail. An attacker controlling a configured proxy or an unintended proxy recipient can observe connection metadata and plaintext HTTP traffic.

## Affected products

- Axios Axios 1.17.0 through 1.18.1

## Identifiers

- CVE-2026-101899
- GHSA-44g4-m2mj-wpvx

## Timeline

- 2026-09-30: disclosed: Advisory published GHSA-44g4-m2mj-wpvx

## Related threats

- [Axios prototype pollution in ToFormData](https://junglewise.ai/threats/cve-2026-101909-axios-is-a-promise-based-http-client-for-the-browser-and-node-js)
- [Axios fetch adapter header injection via prototype pollution](https://junglewise.ai/threats/cve-2026-101908-axios-is-a-promise-based-http-client-for-the-browser-and-node-js)
- [Axios fetch adapter maxRedirects bypass](https://junglewise.ai/threats/cve-2026-101907-axios-is-a-promise-based-http-client-for-the-browser-and-node-js)
- [Axios ReDoS in shouldBypassProxy regular expression](https://junglewise.ai/threats/cve-2026-101906-axios-is-a-promise-based-http-client-for-the-browser-and-node-js)
- [Axios HTTP adapter prototype pollution leading to man-in-the-middle](https://junglewise.ai/threats/cve-2026-101905-axios-is-a-promise-based-http-client-for-the-browser-and-node-js)