CVE-2026-40574
OAuth2 Proxy has an Authorization Bypass in Email Domain Validation via Malformed Multi-@ Email Claims
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.
INFO
Published Date :
April 21, 2026, 5:16 p.m.
Last Modified :
Nov. 11, 2026, 11:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-40574
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update OAuth2 Proxy to version 7.15.2.
- Verify email domain enforcement configuration.
- Validate identity provider email claims.
- Apply strict email syntax checks.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-40574.
| URL | Resource |
|---|---|
| https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-c5c4-8r6x-56w3 | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-40574 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-40574
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-40574 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-40574 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Nov. 11, 2026
Action Type Old Value New Value Added Translation Title: Oauth2-proxy, Description: OAuth2 Proxy es un proxy inverso que proporciona autenticación utilizando proveedores OAuth2. Anterior a la versión 7.15.2, existe un bypass de autorización en OAuth2 Proxy como parte de la opción de aplicación de email_domain. Un atacante podría autenticarse con una declaración de correo electrónico como [email protected]@company.com y satisfacer una verificación de dominio permitido para company.com, aunque la declaración no sea una dirección de correo electrónico válida. El problema SOLO afecta a las implementaciones que dependen de restricciones de email_domain y aceptan valores de declaración de correo electrónico de proveedores de identidad o mapeos de declaraciones que no aplican estrictamente la sintaxis normal de correo electrónico. Esta vulnerabilidad está corregida en la versión 7.15.2. -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'oauth2-proxy', 'product': 'oauth2-proxy', 'versions': [{'status': 'affected', 'version': '< 7.15.2'}]}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-40574', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-04-21T20:18:57.843784Z'} -
Initial Analysis by [email protected]
Apr. 27, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:oauth2_proxy_project:oauth2_proxy:*:*:*:*:*:*:*:* versions up to (excluding) 7.15.2 Added Reference Type GitHub, Inc.: https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-c5c4-8r6x-56w3 Types: Vendor Advisory -
New CVE Received by [email protected]
Apr. 21, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N Added CWE CWE-863 Added Reference https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-c5c4-8r6x-56w3