CVE-2014-4344 in Kerberos
Summary
by MITRE
The acc_ctx_cont function in the SPNEGO acceptor in lib/gssapi/spnego/spnego_mech.c in MIT Kerberos 5 (aka krb5) 1.5.x through 1.12.x before 1.12.2 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via an empty continuation token at a certain point during a SPNEGO negotiation.
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Analysis
by VulDB Data Team • 02/10/2022
The vulnerability identified as CVE-2014-4344 represents a critical denial of service flaw within the MIT Kerberos 5 implementation that affects versions 1.5.x through 1.12.x prior to 1.12.2. This issue specifically targets the acc_ctx_cont function located in the SPNEGO acceptor component at lib/gssapi/spnego/spnego_mech.c. The flaw manifests during the SPNEGO negotiation process when an attacker submits an empty continuation token at a particular stage of authentication, triggering a NULL pointer dereference that ultimately leads to application crash and complete service disruption.
The technical exploitation of this vulnerability occurs within the context of the Simple and Protected GSS-API Negotiation Mechanism which serves as a wrapper for multiple authentication mechanisms including Kerberos. The acc_ctx_cont function handles the continuation of GSS context establishment and fails to properly validate the incoming continuation token before attempting to dereference it. When an empty token is received, the function proceeds to access memory locations that have not been properly initialized, resulting in a NULL pointer dereference that terminates the application process. This behavior aligns with CWE-476 which classifies NULL pointer dereference as a common weakness in software security implementations. The vulnerability demonstrates a classic lack of input validation and error handling that allows malformed data to propagate through the system execution path.
From an operational perspective, this vulnerability presents a significant risk to systems relying on Kerberos authentication services as it enables remote attackers to perform denial of service attacks without requiring authentication credentials. The attack can be executed from any network location capable of communicating with the vulnerable service, making it particularly dangerous for critical infrastructure components that depend on Kerberos for authentication. The impact extends beyond simple service disruption as the application crash can potentially lead to cascading failures in dependent systems, especially in environments where Kerberos is used as a foundational authentication mechanism for enterprise services. The vulnerability affects the availability aspect of the CIA triad by compromising the ability of legitimate users to access services that depend on the compromised Kerberos implementation.
The mitigation strategy for CVE-2014-4344 involves applying the official patch released by MIT Kerberos 5 developers which addresses the NULL pointer dereference by implementing proper validation of continuation tokens before memory access operations. System administrators should immediately upgrade to version 1.12.2 or later to remediate this vulnerability. Additionally, network segmentation and firewall rules can be implemented to limit access to Kerberos services to trusted networks only, reducing the attack surface. Monitoring and logging should be enhanced to detect anomalous authentication patterns that might indicate exploitation attempts. This vulnerability also highlights the importance of proper input validation in security-critical components and aligns with ATT&CK technique T1499.004 which covers network disruption through resource exhaustion and denial of service attacks. Organizations should conduct thorough vulnerability assessments to identify other potential instances of similar flaws in their Kerberos implementations and related security infrastructure components.