OAuth2 Proxy: Health Check User-Agent Matching Bypasses Authentication in auth_request Mode

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Summary

CVECVE-2026-34457
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-14 23:16:28 UTC
Updated2026-04-17 15:38:09 UTC
DescriptionOAuth2 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.

Risk And Classification

Primary CVSS: v3.1 9.1 CRITICAL from [email protected]

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

EPSS: 0.000870000 probability, percentile 0.248480000 (date 2026-04-21)

Problem Types: CWE-290 | CWE-290 CWE-290: Authentication Bypass by Spoofing

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
3.1CNADECLARED9.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Oauth2-proxy Oauth2-proxy affected < 7.15.2 Not specified

References

ReferenceSourceLinkTags
github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-5hvv-m4w4-... [email protected] github.com
github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.15.2 [email protected] github.com
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