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CVE-2026-40574

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

6.8 MediumFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

0.21%Up 0.2 points since Apr 22, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.8

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

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.

Record
CVE-2026-40574
CVSS 3.1
6.8 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-863
Updated
2026-11-02
EUVDEUVD-2026-24175 6.8

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.

Record
EUVD-2026-24175
CVSS 3.1
6.8 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-c5c4-8r6x-56w3 6.8

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

Impact

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. The practical risk ONLY exists in self-hosted or custom OIDC environments and federated setups where unexpected claim values can reach oauth2-proxy. Standard hosted providers that enforce valid email formatting ARE NOT effected.

Patches

Users should upgrade to v7.15.2 or later once available.

Workarounds

The most effective workaround is to ensure the configured identity provider cannot emit malformed or attacker-controlled email claim values.

Record
GHSA-c5c4-8r6x-56w3
CVSS 3.1
6.8 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-863
Updated
2026-11-02
NVD 6.8

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.

Record
CVE-2026-40574
CVSS 3.1
6.8 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-863
Updated
2026-11-02
OSV 6.8

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

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.

Record
CVE-2026-40574
CVSS 3.1
6.8 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-863
Updated
2026-11-02
OSVGHSA-c5c4-8r6x-56w3 6.8

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

Impact

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. The practical risk ONLY exists in self-hosted or custom OIDC environments and federated setups where unexpected claim values can reach oauth2-proxy. Standard hosted providers that enforce valid email formatting ARE NOT effected.

Patches

Users should upgrade to v7.15.2 or later once available.

Workarounds

The most effective workaround is to ensure the configured identity provider cannot emit malformed or attacker-controlled email claim values.

Record
GHSA-c5c4-8r6x-56w3
CVSS 3.1
6.8 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-863
Updated
2026-11-02
OSVBIT-oauth2-proxy-2026-40574 No score

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

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.

Record
BIT-oauth2-proxy-2026-40574
Updated
2026-11-02
OSVGO-2026-5314 No score

OAuth2 Proxy has an Authorization Bypass in Email Domain Validation via Malformed Multi-@ Email Claims in github.com/oauth2-proxy/oauth2-proxy

OAuth2 Proxy has an Authorization Bypass in Email Domain Validation via Malformed Multi-@ Email Claims in github.com/oauth2-proxy/oauth2-proxy

Record
GO-2026-5314
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/oauth2-proxy/oauth2-proxy/v7
Go
 before 7.15.2
7.15.2
oauth2-proxy
Bitnami
 before 7.15.2
7.15.2
github.com/oauth2-proxy/oauth2-proxy
Go
 All versions None known
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-40574 is a medium vulnerability (CVSS 6.8) in Oauth2 Proxy Project Proxy, published April 15, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.21%, the 11th percentile. Fixed in github.com/oauth2-proxy/oauth2-proxy/v7 7.15.2.

References

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