CVE-2026-55602Public exploitNetwork attack vector

Backend routing bypass via host+path substring match

Published Jun 22, 2026 · Updated Jun 22, 2026

Partial string comparison in http-proxy-middleware before 2.0.10, 3.0.6, and 4.1.0 allows remote attackers to reach unintended backends. In getTargetFromProxyTable(), the router concatenates the attacker-controlled Host header and request URL, then uses indexOf() to accept a host+path key anywhere in that combined string rather than requiring an exact host match. The application must enable a router proxy table with a host+path rule; an unauthenticated crafted HTTP request can then cross the intended backend-selection boundary.

CVSS severity6.9
Medium
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Partial string comparison in http-proxy-middleware before 2.0.10, 3.0.6, and 4.1.0 allows remote attackers to reach unintended backends. In getTargetFromProxyTable(), the router concatenates the attacker-controlled Host header and request URL, then uses indexOf() to accept a host+path key anywhere in that combined string rather than requiring an exact host match. The application must enable a router proxy table with a host+path rule; an unauthenticated crafted HTTP request can then cross the intended backend-selection boundary.

The record

CVE
CVE-2026-55602
Published
Jun 22, 2026
Updated
Jun 22, 2026
Vendor
Chimurai
Product
http-proxy-middleware
Classifications
CWE-187, CWE-20, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 22, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 0.16.0, < 2.0.10
  2. Affected versionversion=>= 3.0.0, < 3.0.6
  3. Affected versionversion=>= 4.0.0, < 4.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Chimurai · http-proxy-middlewareversion=>= 0.16.0, < 2.0.10; version=>= 3.0.0, < 3.0.6; version=>= 4.0.0, < 4.1.0

Published CVSS scores

8.6NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
6.9GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-187Partial String Comparison
CWE-20Improper Input Validation
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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