How severe is CVE-2026-40574?

CVE-2026-40574 has a CVSS 3.x base score of 6.8, rated medium severity. It is exploitable over network with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-40574 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-40574?

CVE-2026-40574 affects Oauth2 Proxy Project Oauth2 Proxy. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-40574?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-40574 have an EU (EUVD) identifier?

Yes. CVE-2026-40574 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24175.

When was CVE-2026-40574 published?

CVE-2026-40574 was published on 2026-04-21 and last updated on 2026-06-17.

CVE-2026-40574

CVE-2026-40574 is a medium-severity vulnerability in Oauth2 Proxy Project Oauth2 Proxy with a CVSS 3.x base score of 6.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-863.

Key facts

Severity: Medium (CVSS 3.x base score 6.8)
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-24175
Weakness: CWE-863
Affected product: Oauth2 Proxy Project Oauth2 Proxy
Published: 2026-04-21
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-40574?: 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.
How severe is CVE-2026-40574?: CVE-2026-40574 has a CVSS 3.x base score of 6.8, rated medium severity. It is exploitable over network with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-40574 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-40574?: CVE-2026-40574 affects Oauth2 Proxy Project Oauth2 Proxy. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-40574?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-40574 have an EU (EUVD) identifier?: Yes. CVE-2026-40574 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24175.
When was CVE-2026-40574 published?: CVE-2026-40574 was published on 2026-04-21 and last updated on 2026-06-17.

References

https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-c5c4-8r6x-56w3

Affected products (1)

cpe:2.3:a:oauth2_proxy_project:oauth2_proxy:*:*:*:*:*:*:*:*

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