CVE-2012-1016 in Kerberos
Summary
by MITRE
The pkinit_server_return_padata function in plugins/preauth/pkinit/pkinit_srv.c in the PKINIT implementation in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) before 1.10.4 attempts to find an agility KDF identifier in inappropriate circumstances, which allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted Draft 9 request.
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Analysis
by VulDB Data Team • 05/05/2021
The vulnerability described in CVE-2012-1016 represents a critical denial of service flaw within the PKINIT implementation of MIT Kerberos 5 software. This issue specifically affects the Key Distribution Center (KDC) component where the pkinit_server_return_padata function exhibits improper handling of agility KDF identifiers during authentication requests. The vulnerability manifests when the function attempts to process Draft 9 requests that contain malformed or unexpected KDF identifier parameters, leading to a NULL pointer dereference that ultimately crashes the KDC daemon service.
The technical root cause of this vulnerability stems from inadequate input validation and error handling within the PKINIT pre-authentication mechanism. When a malicious actor submits a crafted Draft 9 request containing inappropriate KDF identifier data, the pkinit_server_return_padata function fails to properly validate the incoming parameters before attempting to dereference pointers associated with these identifiers. This flaw falls under CWE-476 which specifically addresses NULL pointer dereference conditions, making it particularly dangerous as it can be exploited by remote attackers without requiring authentication or privileged access. The function's behavior during this error condition creates a cascading failure that brings down the entire KDC service, effectively preventing legitimate authentication requests from being processed.
The operational impact of this vulnerability extends beyond simple service disruption, as it creates a significant risk to Kerberos infrastructure reliability and availability. Organizations relying on MIT Kerberos 5 for authentication services face potential denial of service attacks that could compromise access to critical network resources, applications, and systems that depend on Kerberos authentication. The daemon crash affects not only individual authentication requests but can potentially disrupt entire authentication domains, impacting business continuity and user access to protected resources. This vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, making it particularly concerning for enterprise environments where Kerberos is extensively deployed for single sign-on and cross-domain authentication scenarios.
Mitigation strategies for CVE-2012-1016 primarily focus on upgrading to patched versions of MIT Kerberos 5, specifically versions 1.10.4 and later where the vulnerability has been addressed through improved input validation and proper error handling mechanisms. System administrators should prioritize patching their Kerberos implementations and implement monitoring solutions to detect anomalous authentication request patterns that might indicate exploitation attempts. Additionally, network segmentation and access controls can help limit the potential impact of such attacks by restricting direct access to KDC services. Organizations should also consider implementing intrusion detection systems that can identify and alert on malformed Draft 9 requests targeting the PKINIT implementation, providing an additional layer of defense against this specific vulnerability class.