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Critical Severity Vulnerability

This vulnerability has been rated as Critical severity. Immediate action is recommended.

CVE-2026-34457

Critical

Low Medium High Critical

9.1

CVSS Score

Published: Apr 14, 2026

Last Modified: Apr 17, 2026

CWE: CWE-290

Vulnerability Description

OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions prior to 7.15.2 contain a configuration-dependent authentication bypass in deployments where OAuth2 Proxy is used with an auth_request-style integration (such as nginx auth_request) and either --ping-user-agent is set or --gcp-healthchecks is enabled. In affected configurations, OAuth2 Proxy treats any request with the configured health check User-Agent value as a successful health check regardless of the requested path, allowing an unauthenticated remote attacker to bypass authentication and access protected upstream resources. Deployments that do not use auth_request-style subrequests or that do not enable --ping-user-agent/--gcp-healthchecks are not affected. This issue is fixed in 7.15.2.

CVSS Metrics

Common Vulnerability Scoring System

Vector String:

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector

Attack Complexity

Privileges Required

User Interaction

Scope

Confidentiality

Integrity

Availability

References & Resources

Severity Details

9.1

out of 10.0

Critical

Weakness Type (CWE)

CWE-290

Authentication Bypass by Spoofing

Description: This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.
Typical Severity: High
Abstraction Level: Base