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.

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

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). 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
```
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

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