CVE-2016-3119 in Kerberos
Summary
by MITRE
The process_db_args function in plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c in the LDAP KDB module in kadmind in MIT Kerberos 5 (aka krb5) through 1.13.4 and 1.14.x through 1.14.1 mishandles the DB argument, which allows remote authenticated users to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted request to modify a principal.
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Analysis
by VulDB Data Team • 07/11/2022
The vulnerability described in CVE-2016-3119 represents a critical denial of service flaw within the LDAP Key Distribution Center (KDB) module of MIT Kerberos 5 authentication system. This issue specifically affects the kadmind daemon which serves as the Kerberos administration server responsible for managing principal accounts and their credentials. The vulnerability resides in the process_db_args function located within plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c, making it particularly dangerous as it targets the core database interaction mechanisms that govern how Kerberos principals are stored and managed within LDAP directories. The flaw impacts versions through 1.13.4 and all 1.14.x releases up to 1.14.1, representing a substantial portion of the Kerberos 5 codebase that was widely deployed in enterprise authentication environments.
The technical nature of this vulnerability stems from improper handling of the DB argument parameter within the process_db_args function, which leads to a NULL pointer dereference condition when processing crafted requests. This occurs during the modification of principal accounts through LDAP-based KDB operations, where authenticated users can exploit the flaw by sending specially crafted requests to the kadmind service. The NULL pointer dereference manifests as a daemon crash, effectively causing a denial of service that renders the Kerberos administration service unavailable to legitimate users. This vulnerability operates at the intersection of improper input validation and memory management errors, creating a condition where the application fails to properly validate or handle database argument parameters before attempting to dereference them. The flaw aligns with CWE-476 which specifically addresses NULL pointer dereference conditions, and represents a classic example of how insufficient parameter validation can lead to service disruption in authentication systems.
The operational impact of this vulnerability extends beyond simple service disruption as it can severely compromise the availability of Kerberos authentication infrastructure. In enterprise environments where Kerberos serves as the primary authentication mechanism for securing network services, a crash of the kadmind daemon can cascade into broader security and operational issues. The vulnerability requires only authenticated access to exploit, meaning that any user with valid Kerberos credentials can potentially trigger the denial of service condition. This makes it particularly dangerous in environments where privilege separation is not properly enforced or where administrative accounts are compromised. The attack vector involves modifying principal accounts, which suggests that the vulnerability could be exploited not just for disruption but potentially as part of a broader attack strategy to weaken authentication infrastructure. From an adversary perspective, this represents a low-effort, high-impact method for causing service degradation in Kerberos environments, aligning with ATT&CK technique T1499.002 for network denial of service attacks.
Mitigation strategies for this vulnerability require immediate patching of affected Kerberos 5 installations to versions that contain the fix for the process_db_args function. Organizations should prioritize updating their kerberos packages and thoroughly test the updates in staging environments before deployment. Additionally, implementing network segmentation and access controls can help limit the potential impact by restricting direct access to kadmind services to only trusted administrative networks. Monitoring for unusual principal modification activities and implementing intrusion detection systems can help identify exploitation attempts. The fix for this vulnerability typically involves proper input validation and null pointer checks within the LDAP database argument processing code, ensuring that all parameters are properly validated before any dereference operations occur. Security teams should also conduct comprehensive audits of their Kerberos deployments to identify all instances of affected versions and ensure complete remediation across their infrastructure, as this vulnerability could potentially be leveraged in combination with other Kerberos-related flaws to create more sophisticated attacks against authentication systems.