Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NSummary
CVE-2026-34457 is a critical-severity Authentication Bypass by Spoofing (CWE-290) vulnerability in Oauth2 Proxy Project Oauth2 Proxy. Its CVSS base score is 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Adversary-in-the-Middle (T1557); ranked at the 39th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to IA-2 (Identification and Authentication (Organizational Users)) and IA-3 (Device Identification and Authentication) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-34457 is a configuration-dependent authentication bypass vulnerability in OAuth2 Proxy, a reverse proxy that provides authentication using OAuth2 providers. It affects versions prior to 7.15.2 when deployed with an auth_request-style integration, such as nginx auth_request, and either the --ping-user-agent flag or --gcp-healthchecks is enabled. In these setups, OAuth2 Proxy treats any request with the configured health check User-Agent value as a successful health check, irrespective of the requested path. The vulnerability is scored at CVSS 9.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N) and is associated with CWE-290 (Authentication Bypass by Spoofing).
An unauthenticated remote attacker can exploit this issue by crafting a request that mimics the health check User-Agent value. This allows the attacker to bypass authentication entirely and gain unauthorized access to protected upstream resources, potentially leading to high confidentiality and integrity impacts without requiring privileges, user interaction, or scope changes. Deployments not using auth_request-style subrequests or without the specified flags enabled remain unaffected.
The vulnerability is addressed in OAuth2 Proxy version 7.15.2, as detailed in the project's release notes and security advisory. Security practitioners should upgrade to this version or later and review configurations to disable unnecessary health check features if auth_request integrations are in use. Relevant details are available at https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.15.2 and https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-5hvv-m4w4-gf6v.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-22761
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 3 hardening rules · 3 OS baselines
V6.4.3V10.4.16V10.5.1V11.4.3
Mitigating Controls (NIST 800-53 r5) AI
Proper unique identification and authentication of users directly stops spoofing-based bypass of authentication.
Device identification and authentication before connection prevents spoofing of devices to bypass auth.
Authentication of non-organizational users blocks external spoofing attempts against the scheme.
Authenticator management ensures credentials cannot be easily spoofed or reused to bypass authentication.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Protecting, conveying, and verifying identity assertions specifically prevents the spoofing that enables authentication bypass.
Requiring authentication of users/services/hardware directly counters spoofing-based bypass when strong methods are used.
Proofing and binding identities reduces spoofing opportunities during enrollment but does not address runtime authentication implementation flaws.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Secure authentication control directly mitigates authentication bypass by spoofing.
Authentication information management directly addresses credential handling that prevents spoofing.
Security testing can detect spoofing vulnerabilities but does not prevent them by itself.
Access control policy reduces spoofing opportunities but does not prescribe authentication mechanisms.
Identity management supports unique identities but does not guarantee resistance to spoofing.
Access rights assignment limits exposure but does not enforce authentication strength.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (1 rule)
- V-248827 OL 8 must not have the rsh-server package installed. prevents CWE-290
RHEL 7 (1 rule)
- V-204442 The Red Hat Enterprise Linux operating system must not have the rsh-server package installed. prevents CWE-290
RHEL 8 (1 rule)
- V-230492 RHEL 8 must not have the rsh-server package installed. prevents CWE-290