CVE-2018-5710 in Kerberos 5
Summary
by MITRE
An issue was discovered in MIT Kerberos 5 (aka krb5) through 1.16. The pre-defined function "strlen" is getting a "NULL" string as a parameter value in plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c in the Key Distribution Center (KDC), which allows remote authenticated users to cause a denial of service (NULL pointer dereference) via a modified kadmin client.
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Analysis
by VulDB Data Team • 10/24/2024
The vulnerability identified as CVE-2018-5710 represents a critical denial of service flaw within the MIT Kerberos 5 authentication system, specifically affecting versions through 1.16. This issue manifests in the Key Distribution Center component where a null pointer dereference occurs due to improper input validation. The vulnerability stems from a fundamental flaw in the ldap_principal2.c plugin file within the KDC module, which processes principal names during authentication operations. When an authenticated attacker manipulates the kadmin client interface, they can inject a null string parameter into the predefined strlen function, triggering the system to attempt dereferencing a null pointer.
The technical exploitation of this vulnerability occurs through the manipulation of the kadmin client interface, which is used for administrative operations within the Kerberos environment. The flaw exists in the LDAP backend plugin implementation where the system fails to validate input parameters before passing them to standard library functions. This particular implementation error demonstrates a classic null pointer dereference vulnerability, which is categorized under CWE-476 in the Common Weakness Enumeration system. The vulnerability allows remote authenticated users to cause the KDC service to crash or terminate unexpectedly, effectively rendering the authentication system unavailable to legitimate users.
The operational impact of CVE-2018-5710 extends beyond simple service disruption, as it can severely compromise the availability of authentication services within organizations relying on MIT Kerberos for secure network authentication. The KDC is a critical component that handles authentication requests and issues tickets to clients, making this vulnerability particularly dangerous in enterprise environments where continuous authentication availability is essential. When exploited, the denial of service condition can persist until the KDC service is manually restarted, potentially causing cascading failures in systems dependent on Kerberos authentication. This vulnerability aligns with ATT&CK technique T1499.004, which involves network denial of service attacks targeting authentication systems, and demonstrates the importance of input validation in security-critical components.
Organizations affected by this vulnerability should implement immediate mitigations including upgrading to patched versions of MIT Kerberos 5, which typically include proper input validation and null pointer checks in the affected ldap_principal2.c file. The recommended approach involves applying the official security patches released by the MIT Kerberos project, which address the root cause by ensuring that null parameters are properly validated before being passed to standard library functions. Additionally, network segmentation and access controls should be implemented to limit the attack surface, as the vulnerability requires authenticated access to the kadmin client interface. System administrators should also monitor for any unusual authentication patterns or service disruptions that might indicate exploitation attempts, and maintain robust backup procedures to ensure rapid recovery from potential service outages. The vulnerability highlights the importance of comprehensive input validation across all security components and demonstrates how seemingly minor implementation flaws can result in significant service availability issues in critical infrastructure systems.