Listen to this Post
CVE-2021-3754 is a security flaw affecting Keycloak identification and access management solutions.
The vulnerability arises from improper input validation during the user registration process.
Specifically, Keycloak allows an attacker to register an account with a specific string.
This string can be crafted to match the email address of an existing legitimate user.
The core issue stems from the order in which user identifiers are processed and validated.
Keycloak evaluates the submitted username before checking the uniqueness of the user’s email.
Because the system treats the input field flexibly, it fails to block email-as-username collisions.
An unauthenticated remote attacker can exploit this behavior directly through public endpoints.
When the malicious registration succeeds, the genuine user’s recovery workflow becomes impaired.
If the legitimate user attempts to reset a forgotten password, the system encounters ambiguity.
Password recovery notifications or reset tokens may be misrouted or blocked entirely.
This prevents the legitimate user from regaining access to their compromised or locked account.
Although the vulnerability does not grant direct remote code execution or data theft,
it severely impacts account availability and operational integrity within the identity provider.
Administrators typically rely on clean separation between usernames and primary email addresses.
When this boundary is crossed, authentication trust models break down significantly.
The issue was originally discovered and disclosed by security researcher Anurag Mondal.
It highlights the importance of rigorous input sanitization and strict uniqueness checks.
Identity management systems must strictly prohibit usernames that duplicate existing user emails.
Failure to implement these checks introduces logical denial-of-service vectors for accounts.
The vulnerability carries a CVSS base score of 5.3, classifying it as a medium-severity issue.
While it requires no special privileges or user interaction, its direct impact is localized.
However, in enterprise environments, account lockouts can lead to administrative overhead.
Security teams must audit user registration endpoints to ensure proper attribute enforcement.
Upstream patches address this flaw by introducing strict validation rules during sign-up.
Organizations running older unsupported versions remain exposed to this logic manipulation.
Applying the latest security updates or vendor-recommended patches mitigates the risk completely.
Understanding this mechanism helps developers secure identity workflows against logical abuses.
DailyCVE Form:
Platform: Keycloak
Version: All versions
Vulnerability: Input validation
Severity: Medium
date: August 2021
Prediction: September 2021
What Undercode Say:
git clone https://github.com/7Ragnarok7/CVE-2021-3754 cd CVE-2021-3754 python3 -m http.server 8080 curl -X POST http://localhost:8080/auth/realms/master/protocol/openid-connect/registrations \ -d "[email protected]&[email protected]&password=secret"
Exploit: (Educational Purposes!)
The exploitation involves sending a crafted registration request to the Keycloak server.
An attacker supplies an existing user’s email address in the username parameter field.
Because input validation lacks cross-field uniqueness enforcement for usernames and emails,
the server accepts the registration and maps the duplicate identity into the database.
Subsequent password reset requests for that email trigger application logic confusion.
The recovery mechanism fails to differentiate between the legitimate owner and the attacker.
Protection: from this CVE
Upgrade Keycloak to the latest patched version provided by Red Hat or upstream releases.
Implement strict custom SPI validators to verify that usernames do not match email formats.
Monitor registration logs for anomalous patterns where usernames resemble email addresses.
Enforce strong account verification policies before activating newly registered user profiles.
Impact:
Loss of account access for legitimate users due to broken password recovery flows.
Potential account confusion and operational disruption within identity management systems.
Increased administrative overhead to resolve locked accounts and investigate anomalies.
🎯Let’s Practice Exploiting & Learn Patching For Free:
🎓 Live Courses & Certifications:
Join Undercode Academy for Verified Certifications
🚀 Request a Custom Project:
Secure, high-velocity infrastructure and disruptive technological engineering. Contact our engineering team for high-tier development and proprietary systems:
[email protected]
💎 Smart Architecture | 🛡️ Secure by Design | ⭐ Trusted by Thousands
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
