dbcve.org
Oauth2 ProxyApplication · Oauth2 Proxy Project

CVE-2026-40574

MEDIUM · 6.8 CVSS v3.1 Published 2026-04-21
Fix available
A fix is available. Upgrade to 7.15.2 or later.
See remediation →
74/100
Remediation priority · Elevated
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

OAuth2 Proxy versions prior to 7.15.2 contain an authorization bypass in the email_domain enforcement feature. Attackers can bypass domain restrictions by providing malformed email claims like [email protected]@company.com, which passes the domain check for company.com despite not being a valid email address. This only affects deployments relying on email_domain restrictions with identity providers or claim mappings that don't enforce strict email syntax.

MitigationUpgrade OAuth2 Proxy to version 7.15.2 or later. Additionally, review identity provider configurations to ensure email claims strictly enforce valid email syntax, and audit existing user access patterns for potential exploitation.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Oauth2 ProxyApplication
Affected:< 7.15.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify OAuth2 Proxy version
    Run 'oauth2-proxy --version' or check the binary version installed in your environment
    Affected if The installed version is below 7.15.2 (e.g., 7.15.1, 7.15.0, earlier versions)
  2. Verify email_domain configuration is in use
    Review your OAuth2 Proxy configuration file (yaml/json) for the 'email_domains' or 'email_domain' setting, or check for '--email-domain' flag in your startup command
    Affected if email_domain or email_domains is configured with one or more allowed domains
  3. Inspect identity provider claim mapping
    Review your identity provider (IdP) configuration (e.g., Azure AD, Okta, Google, Keycloak) to see how email claims are mapped and whether the IdP validates email format strictly
    Affected if The IdP does not enforce strict RFC-compliant email syntax and passes through arbitrary claim values as the email
  4. Audit existing user sessions for malformed emails
    If you have access to logs or user databases, search for email values containing multiple '@' symbols or unusual patterns (e.g., '[email protected]@company.com')
    Affected if Any user records contain malformed email addresses that bypass your intended domain restrictions

You are affected if your OAuth2 Proxy version is below 7.15.2 AND you use email_domain restrictions with an IdP that allows non-strict email claim formats.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 7.15.2 or later
Fixed in 7.15.2
Interim mitigation

Upgrade OAuth2 Proxy to version 7.15.2 or later. Additionally, review identity provider configurations to ensure email claims strictly enforce valid email syntax, and audit existing user access patterns for potential exploitation.

Recommended fix High confidence

7.15.2

  1. Backup your current OAuth2 Proxy configuration and deployment
  2. Review the OAuth2 Proxy 7.15.2 release notes for any configuration or behavioral changes
  3. Upgrade OAuth2 Proxy to version 7.15.2 using your deployment method (package manager, container image, binary, etc.)
  4. After upgrade, verify the email_domain restriction now correctly rejects malformed email claims like '[email protected]@company.com'
  5. Test that legitimate users with valid email addresses in your allowed domains can still authenticate
Caveat Review 7.15.2 release notes for any configuration changes; as with any upgrade, test in staging before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Oauth2 Proxy Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,770
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,832.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-40574 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-40574 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data