CVE-2011-0043 in Windows
Summary
by MITRE
Kerberos in Microsoft Windows XP SP2 and SP3 and Server 2003 SP2 supports weak hashing algorithms, which allows local users to gain privileges by operating a service that sends crafted service tickets, as demonstrated by the CRC32 algorithm, aka "Kerberos Unkeyed Checksum Vulnerability."
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Analysis
by VulDB Data Team • 03/18/2021
The Kerberos Unkeyed Checksum Vulnerability represents a critical security flaw in Microsoft Windows operating systems that affects Windows XP SP2 and SP3 as well as Windows Server 2003 SP2 implementations. This vulnerability stems from the use of weak cryptographic hashing algorithms within the Kerberos authentication protocol, specifically allowing attackers to exploit the absence of proper key derivation and integrity checking mechanisms. The vulnerability manifests when local users can manipulate service tickets through crafted checksums, enabling privilege escalation attacks that bypass normal authentication controls.
The technical exploitation of this vulnerability relies on the implementation of weak hashing algorithms such as CRC32 within the Kerberos authentication framework. According to CWE-327, this represents a weakness in cryptographic implementation where the use of insecure hash functions undermines the security guarantees of the authentication system. The vulnerability occurs because Kerberos in these affected versions does not properly implement keyed checksums, leaving service tickets susceptible to manipulation. Attackers can leverage this weakness by creating malicious service tickets that exploit the predictable nature of CRC32 hashing, allowing them to bypass authentication checks and potentially gain elevated privileges on the target system.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially enable full system compromise when combined with other attack vectors. The vulnerability aligns with ATT&CK technique T1550.003, which describes the use of Kerberoasting to obtain service tickets and perform offline cracking attacks. Local attackers can exploit this weakness to create service tickets that appear legitimate to the Kerberos infrastructure, potentially enabling lateral movement within networks where Kerberos authentication is used. This vulnerability particularly affects enterprise environments where Windows domains rely heavily on Kerberos for authentication, as it undermines the fundamental security assumptions of the authentication protocol.
Mitigation strategies for this vulnerability require immediate patching of affected systems through Microsoft security updates, as the flaw exists in the core authentication implementation. Organizations should implement network segmentation to limit local access privileges and employ monitoring solutions to detect anomalous service ticket usage patterns. The vulnerability demonstrates the importance of cryptographic algorithm selection and proper implementation, as outlined in NIST SP 800-131A guidelines for cryptographic standards. Additionally, organizations should consider implementing additional authentication layers such as multi-factor authentication and regular security assessments to identify similar weaknesses in other cryptographic implementations within their infrastructure.