CVE-2026-55602

http-proxy-middleware `router` host+path substring matching allows Host-header-driven backend routing bypass

State: Published
Severity: 6.9 Medium
Published: Jun 22, 2026
Updated: Jun 23, 2026
Reserved: Jun 16, 2026

Description

http-proxy-middleware is node.js http-proxy middleware. From 0.16.0 until 2.0.10, 3.0.6, and 4.1.0, http-proxy-middleware documents router proxy-table entries as host, path, or host+path selectors, but the host+path implementation uses unanchored substring matching on attacker-controlled request metadata. As a result, a crafted Host header that is only a superstring match for a configured host+path key can still route a request to an unintended backend. This vulnerability is fixed in 2.0.10, 3.0.6, and 4.1.0.

Scores

CVSS	Score	Vector	Source
4.0	6.9 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N	GitHub_M

Weaknesses

CWE-20 Improper Input Validation
CWE-187 Partial String Comparison

Affected Products

Product	Versions
http-proxy-middlewarechimurai	>= 4.0.0, < 4.1.0Affected >= 3.0.0, < 3.0.6Affected >= 0.16.0, < 2.0.10Affected

References

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

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