CVE-2021-3424
Keycloak is vulnerable to IDN homograph attack
A flaw was found in keycloak as shipped in Red Hat Single Sign-On 7.4 where IDN homograph attacks are possible. A malicious user can register himself with a name already registered and trick admin to grant him extra privileges.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
A flaw was found in keycloak as shipped in Red Hat Single Sign-On 7.4 where IDN homograph attacks are possible. A malicious user can register himself with a name already registered and trick admin to grant him extra privileges.
- Record
CVE-2021-3424- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:N/I:P/A:N - Weakness
- CWE-287
- Updated
- 2026-11-02
CVE List No score
A flaw was found in keycloak as shipped in Red Hat Single Sign-On 7.4 where IDN homograph attacks are possible. A malicious user can register himself with a name already registered and trick admin to grant him extra privileges.
- Record
CVE-2021-3424- Weakness
- CWE-287
- Updated
- 2026-11-02
EUVDEUVD-2022-1798 No score
A flaw was found in keycloak as shipped in Red Hat Single Sign-On 7.4 where IDN homograph attacks are possible. A malicious user can register himself with a name already registered and trick admin to grant him extra privileges.
- Record
EUVD-2022-1798- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-pf38-cw3p-22q9
Keycloak is vulnerable to IDN homograph attack
A flaw was found in keycloak as shipped in Red Hat Single Sign-On 7.4 where IDN homograph attacks are possible. A malicious user can register himself with a name already registered and trick admin to grant him extra privileges.
- Record
GHSA-pf38-cw3p-22q9- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-287
- Updated
- 2026-11-02
OSVGHSA-pf38-cw3p-22q9
Keycloak is vulnerable to IDN homograph attack
A flaw was found in keycloak as shipped in Red Hat Single Sign-On 7.4 where IDN homograph attacks are possible. A malicious user can register himself with a name already registered and trick admin to grant him extra privileges.
- Record
GHSA-pf38-cw3p-22q9- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-287
- Updated
- 2026-11-02
OSVRHSA-2021:2063
Red Hat Security Advisory: Red Hat Single Sign-On 7.4.7 security update on RHEL 6
- Record
RHSA-2021:2063- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Updated
- 2026-11-02
OSVRHSA-2021:2064
Red Hat Security Advisory: Red Hat Single Sign-On 7.4.7 security update on RHEL 7
- Record
RHSA-2021:2064- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Updated
- 2026-11-02
OSVRHSA-2021:2065
Red Hat Security Advisory: Red Hat Single Sign-On 7.4.7 security update on RHEL 8
- Record
RHSA-2021:2065- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
org.keycloak:keycloak-servicesMaven |
before 18.0.0 | 18.0.0 |
org.keycloak:keycloak-servicesMaven |
before 18.0.0, plus listed versions 1.0-alpha-11.0-alpha-1-120620131.0-alpha-21.0-alpha-31.0-alpha-4 Show 45 moreShow less1.0-beta-11.0-beta-1-201505211.0-beta-1-201505231.0-beta-21.0-beta-31.0-beta-41.0-final1.0-rc-11.0-rc-21.0.1.Final1.0.2.Final1.0.3.Final1.0.4.Final1.0.5.Final1.1.0.Beta11.1.0.Beta21.1.0.Final1.1.1.Final1.2.0.Beta11.2.0.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.Final |
18.0.0 |
rh-sso7-keycloakRed Hat:red_hat_single_sign_on:7::el6 From an advisory covering 2 CVEs |
before 0:9.0.13-1.redhat_00006.1.el6sso | 0:9.0.13-1.redhat_00006.1.el6sso |
rh-sso7-keycloak-serverRed Hat:red_hat_single_sign_on:7::el6 From an advisory covering 2 CVEs |
before 0:9.0.13-1.redhat_00006.1.el6sso | 0:9.0.13-1.redhat_00006.1.el6sso |
rh-sso7-keycloakRed Hat:red_hat_single_sign_on:7::el7 From an advisory covering 2 CVEs |
before 0:9.0.13-1.redhat_00006.1.el7sso | 0:9.0.13-1.redhat_00006.1.el7sso |
rh-sso7-keycloak-serverRed Hat:red_hat_single_sign_on:7::el7 From an advisory covering 2 CVEs |
before 0:9.0.13-1.redhat_00006.1.el7sso | 0:9.0.13-1.redhat_00006.1.el7sso |
rh-sso7-keycloakRed Hat:red_hat_single_sign_on:7::el8 From an advisory covering 2 CVEs |
before 0:9.0.13-1.redhat_00006.1.el8sso | 0:9.0.13-1.redhat_00006.1.el8sso |
rh-sso7-keycloak-serverRed Hat:red_hat_single_sign_on:7::el8 From an advisory covering 2 CVEs |
before 0:9.0.13-1.redhat_00006.1.el8sso | 0:9.0.13-1.redhat_00006.1.el8sso |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| aliases, products | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-3424 is a medium vulnerability (CVSS 5.3) in Keycloak, published June 1, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.77%, the 55th percentile. Fixed in org.keycloak:keycloak-services 18.0.0.
References
bugzilla.redhat.com/show_bug.cgi?id=1933320
nvd.nist.gov/vuln/detail/CVE-2021-3424
github.com/advisories/GHSA-pf38-cw3p-22q9
access.redhat.com/errata/RHSA-2021:2063
Show 13 moreShow less
security.access.redhat.com/data/csaf/v2/advisories/2021/rhsa-2021_2063.json
cve.org/CVERecord?id=CVE-2021-3424
Left out here: 85 versions. The JSON record has them.