CVE-2004-0371 in Heimdal
Summary
by MITRE
Heimdal 0.6.x before 0.6.1 and 0.5.x before 0.5.3 does not properly perform certain consistency checks for cross-realm requests, which allows remote attackers with control of a realm to impersonate others in the cross-realm trust path.
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Analysis
by VulDB Data Team • 09/02/2019
The vulnerability described in CVE-2004-0371 represents a critical flaw in the Heimdal Kerberos implementation that affects versions 0.6.x before 0.6.1 and 0.5.x before 0.5.3. This issue stems from insufficient validation mechanisms during cross-realm authentication requests, creating a fundamental weakness in the trust relationship between different Kerberos realms. The flaw specifically targets the consistency checking procedures that should validate the integrity of authentication messages when users attempt to authenticate across different trust domains.
The technical implementation of this vulnerability lies in the failure to properly validate cross-realm ticket requests and the absence of adequate cryptographic consistency checks. When a realm receives a cross-realm authentication request, it should verify that the request maintains proper trust path integrity and that the authentication tokens are consistent with the expected cross-realm trust relationships. The Heimdal implementation failed to perform these critical validation steps, allowing malicious actors within a compromised realm to manipulate the authentication process and forge legitimate authentication requests.
This vulnerability operates at the core of Kerberos authentication protocols and falls under the category of credential impersonation attacks. The impact extends beyond simple unauthorized access as it undermines the fundamental trust model that Kerberos relies upon for secure cross-domain authentication. Attackers with control over a single realm can exploit this weakness to impersonate users from trusted realms, effectively breaking the security boundaries that separate different administrative domains. The operational consequences include potential privilege escalation, unauthorized data access, and complete compromise of the cross-realm trust infrastructure.
The vulnerability aligns with CWE-284, which addresses improper access control in authentication systems, and relates to ATT&CK technique T1550.003 for use of Kerberos tickets. Organizations utilizing Heimdal Kerberos implementations in environments with cross-realm trust relationships face significant risk from this vulnerability, as it allows attackers to bypass the security controls designed to protect against unauthorized cross-domain access. The attack vector requires the adversary to have control over at least one realm within the trust path, making it particularly dangerous in environments where multiple administrative domains share trust relationships.
The recommended mitigation strategy involves immediate upgrade to Heimdal versions 0.6.1 or 0.5.3 and later, which contain the necessary consistency checking fixes. Organizations should also implement additional monitoring of cross-realm authentication requests and establish stricter access controls for realms that participate in cross-realm trust relationships. Network segmentation and the implementation of additional authentication layers can provide defense-in-depth measures while the primary vulnerability is being addressed through software updates. Security teams should conduct thorough assessments of their cross-realm trust configurations to identify and remediate any additional weaknesses that may compound the risk from this specific vulnerability.