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CVE-2026-55602— http-proxy-middleware `router` host+path substring matching allows Host-header-driven backend routing bypass

Quick assessment

Affected
chimurai http-proxy-middleware
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

chimurai http-proxy-middleware是chimurai个人开发者开源的一个Node.js的HTTP代理中间件。 Steven Chim http-proxy-middleware 0.16.0版本至2.0.10之前版本、3.0.0版本至3.0.6之前版本和4.0.0版本至4.1.0之前版本存在输入验证错误漏洞，该漏洞源于host+path实现使用未锚定的子字符串匹配攻击者控制的请求元数据，可能导致特制的Host标头将请求路由到非预期的后端。

AI Predicted 6.5 Difficulty: Easy EPSS 0.38% · P32

Possible ATT&CK Techniques 1 AI

T1071.001 · Web Protocols

Affected Version Matrix 3

VendorProduct Version RangeStatus
chimurai http-proxy-middleware >= 4.0.0, < 4.1.0 affected
>= 3.0.0, < 3.0.6 affected
>= 0.16.0, < 2.0.10 affected
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I. Basic Information for CVE-2026-55602

Vulnerability Information
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Vulnerability Title
http-proxy-middleware `router` host+path substring matching allows Host-header-driven backend routing bypass
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Steven Chim http-proxy-middleware 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
chimurai http-proxy-middleware是chimurai个人开发者开源的一个Node.js的HTTP代理中间件。 Steven Chim http-proxy-middleware 0.16.0版本至2.0.10之前版本、3.0.0版本至3.0.6之前版本和4.0.0版本至4.1.0之前版本存在输入验证错误漏洞，该漏洞源于host+path实现使用未锚定的子字符串匹配攻击者控制的请求元数据，可能导致特制的Host标头将请求路由到非预期的后端。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
chimurai http-proxy-middleware >= 4.0.0, < 4.1.0 -

II. Public POCs for CVE-2026-55602

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III. Intelligence Information for CVE-2026-55602

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Vendor Advisories for CVE-2026-55602 (1)

IV. Related Vulnerabilities

Same product: http-proxy-middleware
Same vendor: chimurai
Same weakness: CWE-20