CVE-2009-0844 in Kerberos
Summary
by MITRE
The get_input_token function in the SPNEGO implementation in MIT Kerberos 5 (aka krb5) 1.5 through 1.6.3 allows remote attackers to cause a denial of service (daemon crash) and possibly obtain sensitive information via a crafted length value that triggers a buffer over-read.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 12/29/2024
The vulnerability identified as CVE-2009-0844 represents a critical buffer over-read flaw within the SPNEGO implementation of MIT Kerberos 5 versions 1.5 through 1.6.3. This issue specifically affects the get_input_token function which processes authentication tokens during the Security Negotiation process. The flaw arises when the function encounters a malformed or crafted length value in the SPNEGO token structure, leading to improper memory boundary checks during token processing. The vulnerability falls under CWE-125, which defines buffer over-read conditions where an application reads data past the end of a buffer, potentially exposing sensitive memory contents or causing system instability.
The technical execution of this vulnerability involves an attacker crafting a malicious SPNEGO token with an invalid length field that exceeds the expected buffer boundaries during parsing operations. When the get_input_token function processes this malformed input, it performs memory reads beyond the allocated buffer space, resulting in undefined behavior. This condition can manifest as daemon crashes due to segmentation faults or access violations, while simultaneously potentially leaking sensitive information from adjacent memory locations that may contain credentials, session keys, or other confidential data. The vulnerability is particularly dangerous in networked environments where Kerberos authentication services are exposed to untrusted clients.
From an operational perspective, this vulnerability creates significant risks for organizations relying on MIT Kerberos for authentication services. The denial of service component can disrupt authentication services, potentially affecting thousands of users who depend on Kerberos for secure access to network resources. The information disclosure aspect poses additional security risks as attackers may extract sensitive cryptographic material or authentication data from memory dumps. The impact extends beyond simple service disruption to potential credential compromise and broader authentication system weakening. This vulnerability aligns with ATT&CK technique T1190, which covers exploitation of remote services, and demonstrates how authentication protocol flaws can create cascading security issues within enterprise environments.
Organizations should prioritize immediate patching of affected MIT Kerberos versions to address this vulnerability. The recommended mitigation includes upgrading to patched versions of MIT Kerberos 5, specifically versions 1.6.4 and later where the buffer over-read issue has been resolved through proper input validation and boundary checking mechanisms. System administrators should also implement network segmentation and access controls to limit exposure of Kerberos services to untrusted networks. Monitoring for suspicious authentication patterns and implementing intrusion detection systems can help identify potential exploitation attempts. Additionally, organizations should conduct thorough vulnerability assessments of their Kerberos implementations and consider implementing additional authentication layers or alternative authentication protocols to reduce the attack surface. The fix typically involves strengthening input validation routines and ensuring that all buffer operations include proper bounds checking before memory access occurs, preventing the over-read condition that enables both denial of service and information disclosure attacks.