CVE-2024-21733 is a vulnerability classified under CWE-209, which pertains to the generation of error messages containing sensitive information. It affects Apache Tomcat versions from 8.5.7 through 8.5.63 and 9.0.0-M11 through 9.0.43. The flaw occurs because the server improperly includes sensitive internal information in error messages returned to clients. Such information could include stack traces, configuration details, or other data that an attacker could leverage to gain insights into the system architecture or identify further vulnerabilities. The vulnerability is remotely exploitable without requiring authentication or user interaction, increasing its risk profile. The CVSS v3.1 base score is 5.3 (medium severity), reflecting the vulnerability's potential to disclose confidential information but without direct impact on integrity or availability. No known exploits have been reported in the wild as of the publication date, but the risk remains significant due to the widespread use of Apache Tomcat in enterprise and government web applications. The recommended remediation is to upgrade affected Apache Tomcat instances to versions 8.5.64 or 9.0.44 and later, where the issue has been resolved. Additionally, administrators should audit error handling and logging configurations to ensure sensitive information is not inadvertently exposed.

For European organizations, the primary impact of CVE-2024-21733 is the potential leakage of sensitive information through error messages generated by Apache Tomcat servers. This information disclosure can aid attackers in mapping the internal system environment, identifying software versions, and discovering other vulnerabilities, thereby facilitating more targeted and effective attacks such as privilege escalation, code injection, or denial of service. Given Apache Tomcat's widespread deployment in European enterprises, government agencies, and critical infrastructure sectors, this vulnerability could expose sensitive data or internal architecture details that compromise confidentiality. Although the vulnerability does not directly affect system integrity or availability, the indirect consequences of information leakage can be severe, especially if combined with other vulnerabilities or social engineering attacks. Organizations handling sensitive personal data under GDPR must also consider the regulatory implications of such data exposure. The lack of required authentication and user interaction means attackers can exploit this vulnerability remotely, increasing the risk of automated scanning and exploitation attempts.

1. Upgrade Apache Tomcat instances to version 8.5.64 or 9.0.44 and later immediately to apply the official fix. 2. Review and harden error handling configurations to ensure that error messages do not reveal stack traces, internal paths, or configuration details. 3. Implement centralized logging with access controls to restrict who can view detailed error logs. 4. Use web application firewalls (WAFs) to detect and block suspicious requests that attempt to trigger error conditions. 5. Conduct regular security assessments and penetration tests focusing on error message handling and information leakage. 6. Educate development and operations teams about secure error handling best practices to prevent similar issues in custom applications deployed on Tomcat. 7. Monitor security advisories and threat intelligence feeds for any emerging exploits targeting this vulnerability. 8. If immediate patching is not feasible, consider temporary mitigations such as custom error pages that suppress detailed error information.