CVE-2025-8419 in Keycloak
Summary
by MITRE • 08/06/2025
A vulnerability was found in Keycloak-services. Special characters used during e-mail registration may perform SMTP Injection and unexpectedly send short unwanted e-mails. The email is limited to 64 characters (limited local part of the email), so the attack is limited to very shorts emails (subject and little data, the example is 60 chars). This flaw's only direct consequence is an unsolicited email being sent from the Keycloak server. However, this action could be a precursor for more sophisticated attacks.
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Analysis
by VulDB Data Team • 01/08/2026
CVE-2025-8419 represents a server-side email injection vulnerability affecting Keycloak-services that stems from inadequate input validation during email registration processes. This vulnerability manifests when special characters are utilized in email addresses during user registration, potentially enabling attackers to manipulate the Simple Mail Transfer Protocol (SMTP) communication flow. The flaw resides in the email validation and processing logic where user-provided input containing specific characters such as carriage return and line feed sequences can be interpreted by the SMTP server as command delimiters rather than part of the email address. According to CWE-94, this vulnerability aligns with code injection flaws where untrusted data is improperly incorporated into command or query strings. The technical implementation involves the manipulation of the email local part, which is constrained to 64 characters, limiting the payload to short email messages of approximately 60 characters in length. This constraint significantly limits the attack surface but does not eliminate the potential for exploitation.
The operational impact of this vulnerability extends beyond simple spam generation, as it creates opportunities for more sophisticated attack vectors that align with ATT&CK technique T1192 for exploitation of email injection vulnerabilities. While the immediate consequence is the unauthorized sending of unsolicited emails from the Keycloak server, this capability could serve as a stepping stone for phishing campaigns, spam distribution, or even as a method for exfiltrating information through crafted email payloads. The vulnerability's limited scope to 64-character email addresses means that attackers cannot inject extensive malicious content, but the ability to send unauthorized emails from a legitimate server creates trust issues with email recipients and can damage the reputation of the affected organization. The attack vector requires minimal technical expertise, making it particularly concerning for environments where Keycloak serves as an identity management solution for multiple applications and services.
Mitigation strategies for CVE-2025-8419 should focus on implementing robust input sanitization and validation mechanisms that prevent special characters from being interpreted as SMTP command delimiters during email address processing. Organizations should enforce strict email address format validation that rejects or properly escapes characters that could be interpreted as command sequences within SMTP protocols. The implementation of proper email address normalization and encoding techniques, combined with rate limiting and monitoring of email sending activities, can significantly reduce the risk of exploitation. Additionally, organizations should consider implementing email authentication mechanisms such as SPF, DKIM, and DMARC to help mitigate the impact of any unauthorized email sending activities. Security monitoring should include detection of unusual email sending patterns and unauthorized email delivery attempts from the Keycloak server, as outlined in the MITRE ATT&CK framework for email-related attack techniques. Regular security assessments and penetration testing of identity management systems should be conducted to identify similar vulnerabilities in the email processing pipeline.