CVE-2021-41130Network attack vector

Authorization spoofing via duplicate headers

Published Oct 7, 2021 · Updated Aug 4, 2024

Authentication bypass in Google Cloud Extensible Service Proxy before 1.58.0 allows remote authenticated users to spoof authorization claims. ESPv1 replaces only the first X-Endpoint-API-UserInfo header, allowing a client-supplied duplicate header with a forged JWT claim to reach the backend. Exploitation requires a JWT that ESP accepts and a backend that uses this header for authorization, enabling unauthorized access without direct ESP configuration changes.

CVSS severity5.4
Medium
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Google Cloud Extensible Service Proxy before 1.58.0 allows remote authenticated users to spoof authorization claims. ESPv1 replaces only the first X-Endpoint-API-UserInfo header, allowing a client-supplied duplicate header with a forged JWT claim to reach the backend. Exploitation requires a JWT that ESP accepts and a backend that uses this header for authorization, enabling unauthorized access without direct ESP configuration changes.

The record

CVE
CVE-2021-41130
Published
Oct 7, 2021
Updated
Aug 4, 2024
Vendor
Google Cloud
Product
Extensible Service Proxy
Classifications
CWE-290, T1606
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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=< 1.58.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Google Cloud · Extensible Service Proxyversion=< 1.58.0

Published CVSS scores

6.4GitHub Security AdvisoriesCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
5.4NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
4.9NVDAV:N/AC:M/Au:S/C:P/I:P/A: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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-290Authentication Bypass by Spoofing
T1606Forge Web Credentials

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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