CVE-2004-0642 in Kerberos
Summary
by MITRE
Double free vulnerabilities in the error handling code for ASN.1 decoders in the (1) Key Distribution Center (KDC) library and (2) client library for MIT Kerberos 5 (krb5) 1.3.4 and earlier may allow remote attackers to execute arbitrary code.
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Analysis
by VulDB Data Team • 12/16/2024
The vulnerability described in CVE-2004-0642 represents a critical double free condition within the ASN.1 decoder error handling mechanisms of MIT Kerberos 5 version 1.3.4 and earlier. This flaw exists in two distinct components of the Kerberos authentication system including the Key Distribution Center library and the client library, creating a significant attack surface for remote code execution. The double free vulnerability occurs when memory allocated during ASN.1 decoding operations is freed twice, potentially allowing attackers to manipulate heap memory structures and execute arbitrary code on affected systems.
The technical nature of this vulnerability stems from improper memory management within the Kerberos error handling code paths. When ASN.1 decoding fails during Kerberos authentication processes, the system attempts to free memory resources that have already been freed, creating a condition where attackers can exploit the heap corruption to gain control over program execution flow. This particular weakness aligns with CWE-415, which specifically addresses double free vulnerabilities in memory management. The flaw manifests when the KDC or client library encounters malformed ASN.1 encoded data during authentication negotiations, causing the error handling code to attempt freeing the same memory block twice.
The operational impact of CVE-2004-0642 extends beyond simple privilege escalation to full system compromise, as the vulnerability can be exploited remotely without authentication. Attackers can craft malicious ASN.1 encoded packets that trigger the double free condition during Kerberos authentication, potentially leading to arbitrary code execution with the privileges of the Kerberos service account. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1059 for command and control execution and T1068 for exploit for privilege escalation. The widespread use of Kerberos authentication in enterprise environments means that successful exploitation could compromise entire authentication infrastructures, affecting authentication services, file servers, and network resources that depend on Kerberos for secure access control.
Mitigation strategies for this vulnerability require immediate patching of affected MIT Kerberos 5 installations to versions 1.3.5 and later where the double free conditions have been corrected. Organizations should implement network segmentation to limit exposure of Kerberos services to untrusted networks and consider disabling unnecessary Kerberos services when not required. Additionally, monitoring for abnormal authentication patterns and implementing intrusion detection systems that can identify malformed ASN.1 traffic can help detect exploitation attempts. The vulnerability highlights the importance of proper memory management practices in security-critical code and demonstrates how seemingly minor error handling flaws can result in severe security implications. System administrators should also consider implementing application whitelisting policies to restrict execution of unauthorized code on systems running Kerberos services. The remediation process should include thorough testing of patched systems to ensure that the memory management fixes do not introduce regressions in legitimate Kerberos functionality while maintaining the security posture of the authentication infrastructure.