OAuth2 Proxy has an Authorization Bypass in Email Domain Validation via Malformed Multi-@ Email Claims
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- High
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · High · None
- Fix status
- Partial Red Hat: 1 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-863.
Summary
OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Prior to 7.15.2, an authorization bypass exists in OAuth2 Proxy as part of the email_domain enforcement option. An attacker may be able to authenticate with an email claim such as [email protected]@company.com and satisfy an allowed domain check for company.com, even though the claim is not a valid email address. The issue ONLY affects deployments that rely on email_domain restrictions and accept email claim values from identity providers or claim mappings that do not strictly enforce normal email syntax. This vulnerability is fixed in 7.15.2.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| oauth2-proxy | oauth2-proxy | before 7.15.2 | 7.15.2 | Patch available | CNA |
| — | github.com/oauth2-proxy/oauth2-proxy/v7 (Go) | before 7.15.2 | 7.15.2 | Patch available | GHSA-c5c4-8r6x-56w3 |
- oauth2-proxy Vendoroauth2-proxy Affected before 7.15.2 Fixed in 7.15.2 Patch available CNA
- github.com/oauth2-proxy/oauth2-proxy/v7 (Go) Vendor— Affected before 7.15.2 Fixed in 7.15.2 Patch available GHSA-c5c4-8r6x-56w3
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:oauth2_proxy_project:oauth2_proxy:*:*:*:*:*:*:*:* | before 7.15.2 | Vulnerable | oauth2-proxy |
- cpe:2.3:a:oauth2_proxy_project:oauth2_proxy:*:*:*:*:*:*:*:* Versions before 7.15.2 Vulnerable ·oauth2-proxy
Remediation
- Fix · CNA oauth2-proxy (oauth2-proxy) Fixed in 7.15.2
- Fix · GHSA-c5c4-8r6x-56w3 github.com/oauth2-proxy/oauth2-proxy/v7 (Go) Fixed in 7.15.2 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Ceph Storage 9 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-40574
- 2026-10-03 Alias added: GHSA-c5c4-8r6x-56w3
References
More oauth2-proxy Oauth2 Proxy vulnerabilities
- TI-2025-34353 OAuth2-Proxy has authentication bypass in oauth2-proxy skip_auth_routes due to Query Parameter inclusion CVSS 3.1CRITICAL 9.1
- TI-2026-29315 OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing CVSS 3.1CRITICAL 9.1
- TI-2026-26722 OAuth2 Proxy: Health Check User-Agent Matching Bypasses Authentication in auth_request Mode CVSS 3.1CRITICAL 9.1
- TI-2026-29698 OAuth2 Proxy has an Authentication Bypass via Fragment Confusion in skip_auth_routes and skip_auth_regex CVSS 3.1HIGH 8.2
- TI-2017-14408 CSRF in Bitly oauth2_proxy 2.1 during authentication flow CVSS 3.0HIGH 8.8
- TI-2020-08927 Open Redirect in OAuth2 Proxy CVSS 3.1HIGH 7.1
Sources
- CVE-2026-40574 · CVE Program
- CVE-2026-40574 · NVD
- FIRST EPSS
- GHSA-c5c4-8r6x-56w3 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-40574 · Red Hat security data · CC BY 4.0
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