# CVE-2026-55602: chimurai http-proxy-middleware routing bypass via Host header substring match

Source: https://junglewise.ai/threats/cve-2026-55602-chimurai-http-proxy-middleware-routing-bypass-via-host-header  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-22. Updated: 2026-06-22  
License: CC BY 4.0 with a link back

CVE-2026-55602 · Severity: medium · CVSS 4 · Published 2026-06-22

http-proxy-middleware is a popular tool used by Node.js applications to route web traffic to different backend servers. A flaw in how it handles routing rules allows an attacker to bypass intended traffic restrictions by providing a specially crafted web request. This could result in unauthorized access to internal backend services that were meant to be protected or isolated.

Technologies: [http-proxy-middleware (npm)](https://junglewise.ai/threats/technologies/http-proxy-middleware). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-55602 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55602 being exploited in the wild.

**How severe is CVE-2026-55602?** Medium severity, with a CVSS score of 4, published 22 June 2026.

**Which products and versions are affected?** http-proxy-middleware (npm) SEMVER:introduced=3.0.0,fixed=3.0.6.

**Is there a fix for CVE-2026-55602?** Yes. http-proxy-middleware (npm): upgrade to 3.0.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55602 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-55602?** Check whether you run http-proxy-middleware (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

- http-proxy-middleware (npm): upgrade to 3.0.6 or later

  ```sh
  npm install http-proxy-middleware@3.0.6
  ```


## Technical details

A vulnerability exists in http-proxy-middleware's 'router' configuration when using host+path selectors. The implementation in 'getTargetFromProxyTable()' concatenates the attacker-controlled Host header and request URL, then performs a substring match using 'indexOf()' against the configured routing keys. Because the match is unanchored, an attacker can provide a Host header that is a superstring of a valid routing key (e.g., 'evillocalhost:3000' matching 'localhost:3000'). This allows an attacker to force the proxy to route requests to an unintended backend. The issue is fixed in versions 2.0.10, 3.0.6, and 4.1.0.

## Affected products

- chimurai http-proxy-middleware >= 0.16.0 < 2.0.10, >= 3.0.0 < 3.0.6, >= 4.0.0 < 4.1.0

## Identifiers

- CVE-2026-55602
- GHSA-64mm-vxmg-q3vj

## Timeline

- 2026-06-17: advisory: GitHub Security Advisory published
- 2026-06-22: disclosed: CVE published to NVD

## References

- [https://github.com/chimurai/http-proxy-middleware/security/advisories/GHSA-64mm-vxmg-q3vj](https://github.com/chimurai/http-proxy-middleware/security/advisories/GHSA-64mm-vxmg-q3vj)

## Related threats

- [chimurai http-proxy-middleware CRLF injection in fixRequestBody](https://junglewise.ai/threats/cve-2026-55603-chimurai-http-proxy-middleware-crlf-injection-in-fixrequestbody)
- [http-proxy-middleware double write in fixRequestBody](https://junglewise.ai/threats/cve-2025-32996-http-proxy-middleware-double-write-in-fixrequestbody)
- [http-proxy-middleware fixRequestBody error handling bypass](https://junglewise.ai/threats/cve-2025-32997-http-proxy-middleware-fixrequestbody-error-handling-bypass)
- [http-proxy-middleware denial of service in path filtering](https://junglewise.ai/threats/cve-2024-21536-http-proxy-middleware-denial-of-service-in-path-filtering)