CVE-2025-8419 is a medium-severity vulnerability identified in the Red Hat build of Keycloak version 26.0. The issue arises from improper neutralization of CRLF (Carriage Return Line Feed) sequences during email registration processes, leading to a CRLF injection vulnerability. Specifically, when special characters are used in the local part of an email address during registration, the system fails to properly sanitize these inputs, enabling an attacker to perform SMTP injection. This injection allows the attacker to craft and send short, unsolicited emails from the Keycloak server. The email content is constrained by a 64-character limit on the local part of the email address, which restricts the attack to very short emails, typically including a subject and minimal data (approximately 60 characters). Although the immediate consequence is limited to sending unwanted emails, this behavior could serve as a stepping stone for more complex attacks, such as phishing, spam campaigns, or attempts to exploit other mail server vulnerabilities. The vulnerability does not require authentication or user interaction and can be exploited remotely over the network, increasing its risk profile. The CVSS 3.1 base score is 6.5, reflecting a medium severity level with low complexity of attack and limited impact on confidentiality and integrity, and no impact on availability.

For European organizations using the Red Hat build of Keycloak 26.0, this vulnerability could lead to unauthorized use of their mail infrastructure to send unsolicited emails. This can damage organizational reputation, cause blacklisting of mail servers, and potentially facilitate phishing or social engineering attacks targeting employees or customers. The limited size of injected emails reduces the scope of direct data exfiltration or system compromise, but the ability to send emails from a trusted internal server can be leveraged in multi-stage attacks. Organizations in sectors with strict data protection regulations, such as finance, healthcare, and government, may face compliance risks if this vulnerability is exploited to send malicious emails or spam. Additionally, the vulnerability could be exploited to bypass email filtering systems by originating emails from a legitimate internal source, complicating detection and response efforts.

To mitigate this vulnerability, organizations should promptly apply any patches or updates provided by Red Hat for Keycloak 26.0 once available. In the absence of patches, administrators should implement strict input validation and sanitization on email registration fields to neutralize CRLF sequences and other special characters that could be used for injection. Configuring the mail server to restrict or monitor outbound emails originating from Keycloak can help detect and prevent unauthorized email sending. Implementing rate limiting and anomaly detection on email sending patterns will further reduce risk. Additionally, organizations should review and harden their SMTP server configurations to reject malformed or suspicious emails and employ email authentication protocols such as SPF, DKIM, and DMARC to protect against spoofing. Regular security audits and monitoring of Keycloak logs for unusual registration or email activity are recommended to detect exploitation attempts early.