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Fencer Vulns
medium 6.8

CVE-2026-40574 json

OAuth2 Proxy has an Authorization Bypass in Email Domain Validation via Malformed Multi-@ Email Claims

published 2026-04-15 6 mo ago modified 2026-09-08 2 mo ago also BIT-oauth2-proxy-2026-40574 , EUVD-2026-24175 , GHSA-c5c4-8r6x-56w3 , GO-2026-5314

cvss
6.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 11%
public exploits
0
none known

Summary

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 attacker@evil.com@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.

Patch / fix

  • go github.com/oauth2-proxy/oauth2-proxy/v7 7.15.2
  • bitnami oauth2-proxy 7.15.2
  • oauth2_proxy_project oauth2_proxy 7.15.2
  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-40574 updated cvss 6.8

github.com/oauth2-proxy/oauth2-proxy: OAuth2 Proxy: Authorization Bypass via malicious email claim

  • Red Hat Ceph Storage 9 rhceph/oauth2-proxy-rhel9
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
6 mo ago

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
GitHub 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
OSV 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
go github.com/oauth2-proxy/oauth2-proxy/v7
<7.15.2
7.15.2
bitnami oauth2-proxy
<7.15.2
7.15.2
go github.com/oauth2-proxy/oauth2-proxy
all versions
 no fix listed

Affected products

  • oauth2-proxy oauth2-proxy

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.