CVE-2014-5353 in Kerberos
Summary
by MITRE
The krb5_ldap_get_password_policy_from_dn function in plugins/kdb/ldap/libkdb_ldap/ldap_pwd_policy.c in MIT Kerberos 5 (aka krb5) before 1.13.1, when the KDC uses LDAP, allows remote authenticated users to cause a denial of service (daemon crash) via a successful LDAP query with no results, as demonstrated by using an incorrect object type for a password policy.
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Analysis
by VulDB Data Team • 03/01/2022
The vulnerability CVE-2014-5353 represents a critical denial of service weakness in MIT Kerberos 5 versions prior to 1.13.1, specifically affecting systems where the Key Distribution Center operates through LDAP backend services. This flaw exists within the krb5_ldap_get_password_policy_from_dn function located in plugins/kdb/ldap/libkdb_ldap/ldap_pwd_policy.c, which handles the retrieval of password policies from LDAP directories. The vulnerability manifests when authenticated remote attackers exploit a specific condition where LDAP queries return no results, causing the Kerberos daemon to crash and terminate its operations. The attack vector requires the attacker to be authenticated to the system, making it a privilege escalation scenario that could be leveraged by malicious insiders or compromised accounts.
The technical root cause of this vulnerability stems from inadequate error handling within the LDAP password policy retrieval mechanism. When the krb5_ldap_get_password_policy_from_dn function processes an LDAP query that yields no results, it fails to properly validate or handle the empty response condition. This lack of proper null or empty result checking leads to a segmentation fault or similar memory access violation that crashes the entire Kerberos daemon process. The vulnerability specifically occurs when an incorrect object type is used in the LDAP query, resulting in a query that returns no matching entries. This condition triggers an unhandled code path that ultimately leads to daemon termination. According to CWE classification, this vulnerability maps to CWE-20: Improper Input Validation, as the system fails to properly validate LDAP query responses before proceeding with processing operations. The flaw represents a classic buffer over-read or null pointer dereference scenario where the code assumes the existence of data that may not be present.
The operational impact of CVE-2014-5353 extends beyond simple service disruption, creating significant security implications for organizations relying on Kerberos authentication systems. When the Kerberos daemon crashes due to this vulnerability, it results in complete authentication service failure for all clients attempting to obtain Kerberos tickets, effectively disabling centralized authentication for the entire domain or network segment. This denial of service condition can persist until manual intervention restores the service, potentially taking hours or days depending on the organization's monitoring and response procedures. The vulnerability affects systems where LDAP is used as the backend for storing Kerberos password policies, which is common in enterprise environments where Active Directory or other LDAP directories serve as authentication backends. From an ATT&CK framework perspective, this vulnerability aligns with T1499.004: Endpoint Denial of Service, specifically targeting the Kerberos service as a critical infrastructure component. The impact is particularly severe in environments where Kerberos is used for single sign-on authentication, as the crash can cascade to affect multiple dependent services and applications.
Mitigation strategies for CVE-2014-5353 primarily focus on immediate patching and system hardening measures. Organizations should immediately upgrade to MIT Kerberos 5 version 1.13.1 or later, which contains the necessary fixes for this vulnerability. The patch addresses the improper handling of empty LDAP query results by implementing proper null checking and graceful error handling mechanisms within the krb5_ldap_get_password_policy_from_dn function. Additionally, system administrators should implement monitoring and alerting for Kerberos daemon crashes, as well as establish automated restart procedures for the service to minimize downtime. Network segmentation and access control measures can help limit the attack surface by restricting LDAP query capabilities to only necessary administrative accounts. Organizations should also consider implementing redundant authentication mechanisms and backup Kerberos servers to maintain service availability during potential exploitation attempts. The fix implemented in version 1.13.1 follows secure coding practices by ensuring that all LDAP query responses are properly validated before processing, preventing the daemon from crashing when encountering empty or invalid results. This vulnerability highlights the importance of robust error handling in authentication systems, where failure to properly validate inputs can lead to complete service compromise.