google extensible-service-proxy CVE-2021-41130 is a vulnerability in Google Extensible Service Proxy
Published on October 7, 2021

X-Endpoint-API-UserInfo can be spoofed in cloudendpoints Extensible Service Proxy
Extensible Service Proxy, a.k.a. ESP is a proxy which enables API management capabilities for JSON/REST or gRPC API services. ESPv1 can be configured to authenticate a JWT token. Its verified JWT claim is passed to the application by HTTP header "X-Endpoint-API-UserInfo", the application can use it to do authorization. But if there are two "X-Endpoint-API-UserInfo" headers from the client, ESPv1 only replaces the first one, the 2nd one will be passed to the application. An attacker can send two "X-Endpoint-API-UserInfo" headers, the second one with a fake JWT claim. Application may use the fake JWT claim to do the authorization. This impacts following ESPv1 usages: 1) Users have configured ESPv1 to do JWT authentication with Google ID Token as described in the referenced google endpoint document. 2) Users backend application is using the info in the "X-Endpoint-API-UserInfo" header to do the authorization. It has been fixed by v1.58.0. You need to patch it in the following ways: * If your docker image is using tag ":1", needs to re-start the container to pick up the new version. The tag ":1" will automatically point to the latest version. * If your docker image tag pings to a specific minor version, e.g. ":1.57". You need to update it to ":1.58" and re-start the container. There are no workaround for this issue.

NVD

Vulnerability Analysis

CVE-2021-41130 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality and integrity, and no impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
NONE
Scope:
CHANGED
Confidentiality Impact:
LOW
Integrity Impact:
LOW
Availability Impact:
NONE

Weakness Type

Authentication Bypass by Spoofing

This attack-focused weakness is caused by improperly implemented authentication schemes that are subject to spoofing attacks.


Products Associated with CVE-2021-41130

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Google Extensible Service Proxy
 

Affected Versions

cloudendpoints esp Version < 1.58.0 is affected by CVE-2021-41130

Exploit Probability

EPSS
0.11%
Percentile
29.59%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.