# CVE-2026-42043: Axios NO_PROXY bypass via RFC 1122 loopback subnet addresses

Source: https://junglewise.ai/threats/cve-2026-42043-axios-no-proxy-bypass-via-rfc-1122-loopback-subnet-addresses  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-24. Updated: 2026-06-30  
License: CC BY 4.0 with a link back

CVE-2026-42043 · Severity: high · CVSS 7.2 · Published 2026-04-24

Axios is a widely used library for making web requests in JavaScript applications. A security flaw allows attackers to bypass 'NO_PROXY' settings, which are intended to prevent sensitive internal traffic from being sent through an external proxy server. By using specific local network addresses, an attacker could trick the application into sending internal data to a server they control, potentially exposing private information or internal services.

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-2026-42043 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-42043 being exploited in the wild.

**How severe is CVE-2026-42043?** High severity, with a CVSS score of 7.2, published 24 April 2026.

**Which products and versions are affected?** Axios <= 1.15.0, <= 0.31.0; axios (npm) SEMVER:introduced=1.0.0,fixed=1.15.1.

**Is there a fix for CVE-2026-42043?** Yes. axios (npm): upgrade to 1.15.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-42043 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-42043?** 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 1.15.1 or later

  ```sh
  npm install axios@1.15.1
  ```


## Technical details

Axios contains an incomplete fix for a previous vulnerability (CVE-2025-62718) in its proxy bypass logic. The library's 'isLoopback' function uses a hardcoded set of addresses (localhost, 127.0.0.1, and ::1) to identify local traffic that should bypass a configured proxy. However, it fails to account for the entire 127.0.0.0/8 IPv4 loopback range defined in RFC 1122. An attacker who can control the request URL can use alternative loopback addresses (e.g., 127.0.0.2) to bypass NO_PROXY rules, causing the request to be forwarded to an attacker-controlled proxy. This issue is fixed in versions 1.15.1 and 0.31.1.

## Affected products

- Axios axios <= 1.15.0, <= 0.31.0

## Identifiers

- CVE-2026-42043
- GHSA-pmwg-cvhr-8vh7

## Timeline

- 2026-04-24: disclosed
- 2026-04-24: patched
- 2026-04-24: advisory

## References

- [https://github.com/axios/axios/security/advisories/GHSA-pmwg-cvhr-8vh7](https://github.com/axios/axios/security/advisories/GHSA-pmwg-cvhr-8vh7)
- [https://access.redhat.com/errata/RHSA-2026:14937](https://access.redhat.com/errata/RHSA-2026:14937)
- [https://access.redhat.com/errata/RHSA-2026:16476](https://access.redhat.com/errata/RHSA-2026:16476)
- [https://access.redhat.com/errata/RHSA-2026:16532](https://access.redhat.com/errata/RHSA-2026:16532)
- [https://access.redhat.com/errata/RHSA-2026:16534](https://access.redhat.com/errata/RHSA-2026:16534)
- [https://access.redhat.com/errata/RHSA-2026:16535](https://access.redhat.com/errata/RHSA-2026:16535)
- [https://access.redhat.com/errata/RHSA-2026:16542](https://access.redhat.com/errata/RHSA-2026:16542)

## Related threats

- [Axios NO_PROXY CIDR notation bypass in Node.js adapter](https://junglewise.ai/threats/cve-2026-101899-axios-cidr-form-no-proxy-entries-are-ignored-causing-proxy)
- [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)