Apache Tomcat mod_jk Connector: Vulnerability Enables Security Bypass or Information Disclosure

A medium-severity vulnerability has been identified in the Apache Tomcat mod_jk Connector, a module used to connect the Apache HTTP Server with Apache Tomcat. This flaw can be exploited by a remote, unauthenticated attacker to either bypass security mechanisms or disclose confidential information. The specific nature of the vulnerability involves how mod_jk processes incoming requests, potentially leading to misinterpretation of access controls or unintended exposure of internal data. This puts organizations using Apache HTTP Server as a frontend proxy to Tomcat, particularly those relying on mod_jk for secure routing, at risk of unauthorized access to application resources, sensitive configuration details, or other internal information. The vulnerability does not specify a particular version, implying that all versions of the mod_jk connector may be affected until a patch is released.

Attack Chain

1. An unauthenticated attacker performs reconnaissance to identify web servers running Apache HTTP Server acting as a frontend for Apache Tomcat, utilizing the mod_jk connector.
2. The attacker identifies a weakness in mod_jk's request handling, potentially through malformed HTTP headers, URL paths, or request parameters.
3. The attacker crafts a specialized HTTP request designed to exploit this vulnerability.
4. The malicious HTTP request is sent to the Apache HTTP Server, which then forwards it to the mod_jk connector.
5. Due to the vulnerability, the mod_jk connector misinterprets the crafted request, leading to an unintended security bypass or an information disclosure event.
6. The Apache Tomcat backend processes the misinterpreted request, granting the attacker unauthorized access to internal resources or returning sensitive data in the HTTP response.
7. The attacker receives confidential information (e.g., configuration files, internal application data, session tokens) or gains access to restricted application functionalities (e.g., administrative interfaces).

Impact

Successful exploitation of this vulnerability can lead to significant unauthorized access and data breaches. Attackers could bypass authentication or authorization controls, gaining access to sensitive application components or internal network segments. The disclosure of information could include critical system configurations, proprietary application data, user credentials, or other confidential business information. The full extent of impact depends on the nature of the information disclosed or the access gained, potentially leading to further compromise of the affected system and associated backend services.

Recommendation

• Consult the Apache Tomcat project's official security advisories for patches or mitigation steps for mod_jk Connector.
• Implement robust monitoring of web server access logs and Tomcat application logs for unusual request patterns, access to sensitive endpoints, or large data transfers originating from unauthenticated sessions.
• Review and harden mod_jk and Tomcat configurations to ensure least privilege access and restrict internal resource exposure.