#VU77751 Input validation error in Keycloak - CVE-2021-3754

Vulnerability identifier: #VU77751

Vulnerability risk: Low

CVSSv4.0: 5.5 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P/U:Clear]

CVE-ID: CVE-2021-3754

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
Keycloak
Server applications / Directory software, identity management

Vendor: Keycloak

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient validation of user-supplied input. A remote attacker can register himself with the username same as the email ID of any existing user and perform a denial of service (DoS) attack.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Keycloak: before 24.0.1, 24.0.1

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External links
https://access.redhat.com/security/cve/CVE-2021-3754
https://bugzilla.redhat.com/show_bug.cgi?id=1999196
https://github.com/keycloak/keycloak/security/advisories/GHSA-4vc8-pg5c-vg4x

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.