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CVE-2021-3827

ECP SAML binding bypasses authentication flows

6.8 MediumFix available

A flaw was found in keycloak, where the default ECP binding flow allows other authentication flows to be bypassed. By exploiting this behavior, an attacker can bypass the MFA authentication by sending a SOAP request with an AuthnRequest and Authorization header with the user's credentials. The highest threat from this vulnerability is to confidentiality and integrity.

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

1.11%Up 0.2 points since Aug 24, 2022
90%50%10%1%

What each source reports

NVD Score used 6.8

A flaw was found in keycloak, where the default ECP binding flow allows other authentication flows to be bypassed. By exploiting this behavior, an attacker can bypass the MFA authentication by sending a SOAP request with an AuthnRequest and Authorization header with the user's credentials. The highest threat from this vulnerability is to confidentiality and integrity.

Record
CVE-2021-3827
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-287
Updated
2026-11-02
CVE List No score

A flaw was found in keycloak, where the default ECP binding flow allows other authentication flows to be bypassed. By exploiting this behavior, an attacker can bypass the MFA authentication by sending a SOAP request with an AuthnRequest and Authorization header with the user's credentials. The highest threat from this vulnerability is to confidentiality and integrity.

Record
CVE-2021-3827
Weakness
CWE-287
Updated
2026-11-02
EUVDEUVD-2022-1622 No score

A flaw was found in keycloak, where the default ECP binding flow allows other authentication flows to be bypassed. By exploiting this behavior, an attacker can bypass the MFA authentication by sending a SOAP request with an AuthnRequest and Authorization header with the user's credentials. The highest threat from this vulnerability is to confidentiality and integrity.

Record
EUVD-2022-1622
Updated
2026-11-03
GitHub AdvisoriesGHSA-4pc7-vqv5-5r3v 8.1

ECP SAML binding bypasses authentication flows

Description

A flaw was found in keycloak, where the default ECP binding flow allows other authentication flows to be bypassed. By exploiting this behavior an attacker can bypass the MFA authentication by sending a SOAP request with an AuthnRequest and Authorization header with the user's credentials. The highest threat from this vulnerability is to confidentiality and integrity.

Record
GHSA-4pc7-vqv5-5r3v
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287
Updated
2026-11-02
OSV 6.8

A flaw was found in keycloak, where the default ECP binding flow allows other authentication flows to be bypassed. By exploiting this behavior, an attacker can bypass the MFA authentication by sending a SOAP request with an AuthnRequest and Authorization header with the user's credentials. The highest threat from this vulnerability is to confidentiality and integrity.

Record
CVE-2021-3827
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
OSVGHSA-4pc7-vqv5-5r3v 8.1

ECP SAML binding bypasses authentication flows

Description

A flaw was found in keycloak, where the default ECP binding flow allows other authentication flows to be bypassed. By exploiting this behavior an attacker can bypass the MFA authentication by sending a SOAP request with an AuthnRequest and Authorization header with the user's credentials. The highest threat from this vulnerability is to confidentiality and integrity.

Record
GHSA-4pc7-vqv5-5r3v
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287
Updated
2026-11-02
OSVRHSA-2022:0151 8.3

Red Hat Security Advisory: Red Hat Single Sign-On 7.5.1 security update on RHEL 7

Record
RHSA-2022:0151
CVSS 3.1
8.3 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H
Updated
2026-11-02
OSVRHSA-2022:0152 8.3

Red Hat Security Advisory: Red Hat Single Sign-On 7.5.1 security update on RHEL 8

Record
RHSA-2022:0152
CVSS 3.1
8.3 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
org.keycloak:keycloak-saml-core
Maven
 before 18.0.0
18.0.0
org.keycloak:keycloak-saml-core
Maven
 before 18.0.0, plus listed versions
1.1.0.Beta11.1.0.Beta21.1.0.Final1.1.1.Final1.2.0.Beta1
Show 45 moreShow less
1.2.0.CR11.2.0.Final1.3.0.Final1.3.1.Final1.4.0.Final1.5.0-Final1.5.0.Final1.5.1.Final1.6.0.Final1.6.1.Final1.7.0.CR11.7.0.Final1.8.0.Alpha11.8.0.CR11.8.0.CR21.8.0.CR31.8.0.Final1.8.1.Final1.9.0.CR11.9.0.Final1.9.1.Final1.9.2.Final1.9.3.Final1.9.4.Final1.9.5.Final1.9.7.Final1.9.8.Final10.0.010.0.110.0.211.0.011.0.111.0.211.0.312.0.012.0.112.0.212.0.312.0.413.0.013.0.114.0.015.0.015.0.115.0.2
18.0.0
rh-sso7-keycloak
Red Hat:red_hat_single_sign_on:7.5::el7
From an advisory covering 4 CVEs
 before 0:15.0.4-1.redhat_00001.1.el7sso
0:15.0.4-1.redhat_00001.1.el7sso
rh-sso7-keycloak-server
Red Hat:red_hat_single_sign_on:7.5::el7
From an advisory covering 4 CVEs
 before 0:15.0.4-1.redhat_00001.1.el7sso
0:15.0.4-1.redhat_00001.1.el7sso
rh-sso7-keycloak
Red Hat:red_hat_single_sign_on:7.5::el8
From an advisory covering 4 CVEs
 before 0:15.0.4-1.redhat_00001.1.el8sso
0:15.0.4-1.redhat_00001.1.el8sso
rh-sso7-keycloak-server
Red Hat:red_hat_single_sign_on:7.5::el8
From an advisory covering 4 CVEs
 before 0:15.0.4-1.redhat_00001.1.el8sso
0:15.0.4-1.redhat_00001.1.el8sso

History

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

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

In short

CVE-2021-3827 is a medium vulnerability (CVSS 6.8) in Keycloak, published April 27, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.11%, the 66th percentile. Fixed in org.keycloak:keycloak-saml-core 18.0.0.

References

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