CVE-2008-0063 in Kerberos
Summary
by MITRE
The Kerberos 4 support in KDC in MIT Kerberos 5 (krb5kdc) does not properly clear the unused portion of a buffer when generating an error message, which might allow remote attackers to obtain sensitive information, aka "Uninitialized stack values."
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Analysis
by VulDB Data Team • 08/07/2019
The vulnerability identified as CVE-2008-0063 represents a critical information disclosure flaw within the Kerberos 5 Key Distribution Center implementation. This issue specifically affects the Kerberos 4 compatibility layer that exists within the MIT Kerberos 5 software suite, where the krb5kdc daemon processes authentication requests. The flaw manifests when the system generates error messages that contain uninitialized stack memory values, creating potential exposure of sensitive data that was previously stored in the affected memory regions.
The technical root cause of this vulnerability lies in improper memory management practices during error message construction within the Kerberos 4 support code path. When the KDC processes authentication requests and encounters errors, it constructs error responses that include portions of stack memory that were not explicitly cleared or initialized. This occurs because the buffer handling logic fails to zero out unused portions of memory before populating error messages, leaving remnants of previous data accessible to attackers. The vulnerability is classified under CWE-248 as an "Uninitialized Variable" and specifically relates to improper handling of stack memory allocation in cryptographic authentication systems.
The operational impact of this vulnerability extends significantly within environments utilizing MIT Kerberos 5 with Kerberos 4 compatibility enabled. Remote attackers who can send malformed Kerberos 4 requests to the KDC can potentially intercept error responses and extract sensitive information from the uninitialized stack memory. This information might include cryptographic keys, session tokens, user credentials, or other confidential data that was previously stored in the affected memory areas. The attack vector requires network access to the KDC service and does not necessitate authentication, making it particularly dangerous in networked environments where Kerberos services are exposed to untrusted networks.
Security implications of this vulnerability align with ATT&CK technique T1552.001 for "Unsecured Credentials" and T1005 for "Data from Local System." Organizations running affected MIT Kerberos 5 implementations face potential compromise of their authentication infrastructure, as attackers could leverage this weakness to gain additional information that could be used for further attacks or credential theft. The vulnerability demonstrates the critical importance of proper memory initialization practices in security-sensitive code, particularly within cryptographic protocols where information disclosure can lead to complete system compromise. The flaw affects systems where Kerberos 4 compatibility is enabled, making it relevant to legacy environments that have not yet migrated to modern Kerberos 5 authentication mechanisms.
Mitigation strategies for this vulnerability require immediate patching of affected MIT Kerberos 5 installations to versions that properly clear memory buffers before error message construction. Organizations should also implement network segmentation to limit access to KDC services, disable Kerberos 4 compatibility where possible, and monitor network traffic for suspicious error message patterns. Additional defensive measures include regular security assessments of authentication infrastructure, implementation of intrusion detection systems monitoring for unusual authentication error patterns, and comprehensive network access controls restricting direct KDC exposure to trusted networks only. The vulnerability underscores the necessity of thorough memory management practices in security-critical applications and the importance of maintaining up-to-date cryptographic software implementations.