CVE-2026-40574 OAuth2 Proxy has an Authorization Bypass in Email Domain Validation via Malformed Multi-@ Email Claims
Attackers can bypass email domain restrictions in OAuth2 Proxy by using malformed email claims, allowing unauthorized access if email_domain enforcement is enabled.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40574?
CVE-2026-40574 is a medium-severity authentication bypass vulnerability in oauth2-proxy, published on 21 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Weakness: CWE-863
Which versions are affected by CVE-2026-40574?
5 open source packages ship an affected version, including github.com/oauth2-proxy/oauth2-proxy/v7, oauth2-proxy and github.com/oauth2-proxy/oauth2-proxy. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/oauth2-proxy/oauth2-proxy/v7 Go | All versions | 7.15.2 |
github.com/oauth2-proxy/oauth2-proxy/v7 Go | All versions | 7.15.2 |
github.com/oauth2-proxy/oauth2-proxy/v7 Go | All versions | 7.15.2 |
oauth2-proxy Bitnami | All versions | 7.15.2 |
github.com/oauth2-proxy/oauth2-proxy Go | All versions | None |
Products include Oauth2 Proxy Project Oauth2 Proxy.
How do I fix CVE-2026-40574?
Upgrade github.com/oauth2-proxy/oauth2-proxy/v7 to 7.15.2 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-40574 being exploited?
There is no known exploitation of CVE-2026-40574 in the wild and no public exploit code.
Other vulnerabilities in oauth2-proxy
- CVE-2026-40575 OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing
- CVE-2026-34457 OAuth2 Proxy: Health Check User-Agent Matching Bypasses Authentication in auth_request Mode
- CVE-2025-54576 OAuth2-Proxy has authentication bypass in oauth2-proxy skip_auth_routes due to Query Parameter inclusion
- CVE-2017-1000069 Cross-site Request Forgery (CSRF)
- CVE-2026-41059 OAuth2 Proxy has an Authentication Bypass via Fragment Confusion in skip_auth_routes and skip_auth_regex
Sources
Also known as BIT-oauth2-proxy-2026-40574, GHSA-c5c4-8r6x-56w3, GO-2026-5314, MINI-3rhc-mr2m-h438, MINI-f472-6mpw-qvxp.