CVE-2011-0284 in Kerberos
Summary
by MITRE
Double free vulnerability in the prepare_error_as function in do_as_req.c in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) 1.7 through 1.9, when the PKINIT feature is enabled, allows remote attackers to cause a denial of service (daemon crash) or possibly execute arbitrary code via an e_data field containing typed data.
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Analysis
by VulDB Data Team • 12/29/2024
The CVE-2011-0284 vulnerability represents a critical double free error in the Key Distribution Center implementation of MIT Kerberos 5 versions 1.7 through 1.9. This flaw exists within the prepare_error_as function located in the do_as_req.c source file, specifically when the PKINIT (Public Key Cryptography for Initial Authentication in Kerberos) feature is enabled. The vulnerability manifests when processing an e_data field containing typed data, creating a scenario where memory management becomes compromised through improper deallocation of the same memory block twice. The double free condition arises from the function's failure to properly validate or handle the memory allocation lifecycle during error processing, particularly when dealing with PKINIT authentication requests that contain malformed typed data structures.
The technical exploitation of this vulnerability occurs during the Kerberos authentication process when a malicious attacker submits a specially crafted PKINIT request containing malformed e_data field content. When the KDC processes this request through the prepare_error_as function, the flawed memory management logic leads to the same memory pointer being freed twice, which can result in heap corruption. This heap corruption creates opportunities for attackers to manipulate the program's execution flow, potentially leading to arbitrary code execution on the vulnerable KDC server. The vulnerability's impact is significant because the KDC serves as a critical infrastructure component in Kerberos authentication systems, making successful exploitation capable of causing widespread service disruption or system compromise.
The operational impact of CVE-2011-0284 extends beyond simple denial of service to potentially enable remote code execution, making it a severe security concern for organizations relying on Kerberos authentication. The vulnerability affects the core authentication infrastructure, potentially allowing attackers to gain unauthorized access to sensitive network resources, escalate privileges, or disrupt authentication services for entire domains. Organizations using MIT Kerberos 5 versions 1.7 through 1.9 with PKINIT enabled face substantial risk, as the attack vector requires only network access to submit malicious requests to the KDC service. This vulnerability aligns with CWE-415, which describes double free conditions in memory management, and represents a classic example of how improper memory handling can lead to critical security implications in authentication systems.
Mitigation strategies for CVE-2011-0284 primarily involve immediate patching of affected MIT Kerberos 5 installations to versions that address the double free vulnerability in the prepare_error_as function. Organizations should also consider disabling PKINIT functionality if it is not essential for their authentication requirements, as this removes the attack surface entirely. Network segmentation and access controls can help limit exposure by restricting direct access to KDC services from untrusted networks. Security monitoring should focus on detecting unusual authentication patterns or service disruptions that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper memory management in security-critical components and highlights the need for thorough code review processes, particularly for functions handling error conditions and memory allocation in authentication systems. This issue relates to ATT&CK technique T1550.001, which covers use of valid accounts for initial access, as compromised KDC services could provide attackers with elevated privileges within the Kerberos domain.
The vulnerability underscores the critical nature of memory safety in authentication infrastructure components and the potential for seemingly minor code flaws to create significant security risks. Organizations should conduct comprehensive vulnerability assessments to identify all instances of affected MIT Kerberos versions and ensure complete remediation. Regular security updates and proper configuration management become essential practices for maintaining secure Kerberos deployments, particularly given the foundational role these services play in enterprise authentication systems. The flaw also demonstrates the importance of robust input validation and error handling in cryptographic authentication protocols, where malformed data processing can lead to memory corruption vulnerabilities that compromise system integrity and security.