CVE-2007-4743 in Kerberos
Summary
by MITRE
The original patch for CVE-2007-3999 in svc_auth_gss.c in the RPCSEC_GSS RPC library in MIT Kerberos 5 (krb5) 1.4 through 1.6.2, as used by the Kerberos administration daemon (kadmind) and other applications that use krb5, does not correctly check the buffer length in some environments and architectures, which might allow remote attackers to conduct a buffer overflow attack.
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Analysis
by VulDB Data Team • 04/21/2019
The vulnerability described in CVE-2007-4743 represents a critical buffer overflow flaw within the RPCSEC_GSS RPC library implementation in MIT Kerberos 5 versions 1.4 through 1.6.2. This issue emerged as an incomplete fix for the earlier vulnerability CVE-2007-3999, which itself was a significant security weakness in the Kerberos authentication system. The flaw specifically affects the svc_auth_gss.c component that handles GSS (Generic Security Services) authentication for RPC services, making it particularly dangerous as it impacts the core authentication mechanisms used by kadmind and other Kerberos-dependent applications. The vulnerability manifests due to improper buffer length validation during authentication processing, creating a potential attack surface where remote adversaries can exploit memory corruption vulnerabilities.
The technical implementation flaw occurs in the buffer handling logic within the GSS authentication subsystem where the system fails to properly validate input buffer sizes before processing authentication tokens. This oversight allows attackers to craft specially malformed authentication requests that exceed the allocated buffer boundaries, leading to memory corruption that can be exploited for arbitrary code execution. The vulnerability is architecture and environment dependent, meaning it may not manifest consistently across all systems, but when triggered, it provides attackers with the ability to overwrite adjacent memory locations, potentially leading to privilege escalation or complete system compromise. The flaw directly relates to CWE-121, which addresses stack-based buffer overflow conditions, and represents a classic example of inadequate input validation in security-critical code paths.
The operational impact of this vulnerability extends far beyond simple authentication failures, as it compromises the fundamental security model of Kerberos-based authentication systems. Attackers exploiting this vulnerability can potentially gain unauthorized access to administrative functions within Kerberos environments, undermining the entire trust model that Kerberos is designed to establish. The vulnerability affects not just kadmind but any application that relies on krb5's RPCSEC_GSS implementation for secure communication, making it particularly dangerous in enterprise environments where Kerberos is widely deployed for single sign-on and authentication services. Systems using older krb5 versions are at significant risk, as the original patch for CVE-2007-3999 was insufficient to address all possible buffer length scenarios across different hardware architectures and system configurations.
Organizations should prioritize immediate remediation by upgrading to patched versions of MIT Kerberos 5, specifically versions 1.6.3 or later where the buffer length validation has been properly implemented. The mitigation strategy should include comprehensive network monitoring to detect potential exploitation attempts, as well as implementing additional authentication layers and access controls to limit the impact of any successful attacks. System administrators should also consider implementing intrusion detection systems that can identify malformed GSS authentication requests that may indicate exploitation attempts. The vulnerability highlights the importance of thorough testing of security patches across different environments and architectures, as demonstrated by the fact that the initial fix for CVE-2007-3999 was inadequate. This issue also aligns with ATT&CK technique T1566, which covers credential harvesting through network-based attacks, as successful exploitation could lead to unauthorized access to Kerberos credentials and associated privileged accounts.