CVE-2012-3546 in Tomcat
Summary
by MITRE
org/apache/catalina/realm/RealmBase.java in Apache Tomcat 6.x before 6.0.36 and 7.x before 7.0.30, when FORM authentication is used, allows remote attackers to bypass security-constraint checks by leveraging a previous setUserPrincipal call and then placing /j_security_check at the end of a URI.
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Analysis
by VulDB Data Team • 04/19/2021
The vulnerability described in CVE-2012-3546 represents a critical authentication bypass flaw within Apache Tomcat's realm-based security implementation. This issue specifically affects versions prior to 6.0.36 and 7.0.30, where the FORM authentication mechanism fails to properly validate user credentials when a previous setUserPrincipal call has already been established. The vulnerability stems from improper handling of security constraints within the RealmBase.java component, which is responsible for managing user authentication and authorization in the servlet container. Attackers can exploit this weakness by manipulating the request URI to include the /j_security_check endpoint, effectively circumventing the intended security checks that should validate user credentials before granting access to protected resources.
The technical implementation of this vulnerability involves a specific sequence of events that exploits a design flaw in Tomcat's authentication flow. When a user initially authenticates through FORM authentication, the system may establish a principal context through the setUserPrincipal method. However, the subsequent validation logic fails to properly verify whether the current request should be subject to security constraints, particularly when the URI ends with /j_security_check. This flaw creates a window where attackers can manipulate the authentication state and bypass the normal security constraint enforcement mechanisms that would typically require proper credential validation. The vulnerability is particularly concerning because it operates at the core authentication layer of the web application server, affecting the fundamental security model that protects application resources.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can enable attackers to gain unauthorized access to protected application resources without proper authentication. This authentication bypass can lead to data exposure, privilege escalation, and potential system compromise depending on the application's security model and the resources being protected. The vulnerability is particularly dangerous in environments where sensitive data processing occurs, as it could allow attackers to access restricted administrative functions, user data, or business-critical information. Security constraints that are meant to protect specific application paths or resources become ineffective, potentially exposing the entire application to unauthorized access. The attack vector is relatively simple and can be executed remotely without requiring special privileges or access to the system itself, making it particularly attractive to threat actors seeking to exploit web application vulnerabilities.
Organizations affected by this vulnerability should immediately implement mitigations including upgrading to the patched versions of Apache Tomcat 6.0.36 and 7.0.30, or applying the appropriate security patches. Additionally, administrators should review their application security configurations and ensure that proper authentication mechanisms are in place to prevent similar issues. The vulnerability aligns with CWE-284, which describes improper access control, and maps to ATT&CK technique T1078 for valid accounts and T1566 for malicious file execution, as attackers could leverage this bypass to gain elevated privileges and execute malicious code within the application context. Security monitoring should be enhanced to detect unusual authentication patterns and URI manipulation attempts that could indicate exploitation of this vulnerability. Organizations should also conduct comprehensive security assessments of their web application environments to identify any other potential authentication bypass vulnerabilities that could be exploited in similar ways, ensuring that their security controls properly enforce access restrictions regardless of the authentication state or previous principal assignments.