CVE-2026-40574Medium· 6.8▾ SunlitOAuth2 Proxy has an Authorization Bypass in Email Domain Validation via Malformed Multi-@ Email Claims
▾ Sunlit zone — Low / medium · no exploitation signal
impact 37.4 · likelihood 0 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 31.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
Last analysed / modified upstream
0.2%
0.2% → 0.3%
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. The practical risk ONLY exists in self-hosted or custom OIDC environments and federated setups where unexpected claim values can reach oauth2-proxy. Standard hosted providers that enforce valid email formatting ARE NOT effected.
Users should upgrade to v7.15.2 or later once available.
The most effective workaround is to ensure the configured identity provider cannot emit malformed or attacker-controlled email claim values.
github.com/oauth2-proxy/oauth2-proxy/v7 < 7.15.2Upgrade to a patched release:
github.com/oauth2-proxy/oauth2-proxy/v7 7.15.2Connected by shared product, vendor, weakness, or advisory.
CVE-2026-40575Critical· 9.1OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing
CVE-2021-21411Medium· 5.5OAuth2-Proxy's `--gitlab-group` GitLab Group Authorization config flag stopped working in v7.0.0
CVE-2021-21291Medium· 5.4Subdomain checking of whitelisted domains could allow unintended redirects in oauth2-proxy
CVE-2026-76835Critical· 9.1OAuth2 Proxy honours a client-supplied X-Forwarded-Uri header when deciding whether a request may skip authentication, because the guard added for CVE-2026-40575 is inert in the default reverse-proxy configuration
CVE-2020-5233Medium· 5.9The pattern '/\domain.com' is not disallowed when redirecting, allowing for open redirect
CVE-2020-4037Medium· 4.3Open Redirect in OAuth2 Proxy