CVE-2000-0843 in pam_smb
Summary
by MITRE
Buffer overflow in pam_smb and pam_ntdom pluggable authentication modules (PAM) allow remote attackers to execute arbitrary commands via a login with a long user name.
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Analysis
by VulDB Data Team • 05/11/2019
The vulnerability identified as CVE-2000-0843 represents a critical buffer overflow flaw within the pluggable authentication modules (PAM) of the samba software suite. This issue specifically affects the pam_smb and pam_ntdom modules which are responsible for authentication processes in network environments utilizing samba services. The flaw stems from inadequate input validation mechanisms that fail to properly handle excessively long user names during the authentication process, creating a condition where malicious actors can exploit memory corruption vulnerabilities to gain unauthorized system access.
The technical implementation of this vulnerability occurs when a remote attacker submits an authentication request containing a user name that exceeds the allocated buffer size within the PAM modules. This buffer overflow condition allows the attacker to overwrite adjacent memory locations, potentially including return addresses and control data structures within the program execution stack. According to CWE classification, this represents a classic buffer overflow vulnerability categorized under CWE-121, which specifically addresses stack-based buffer overflow conditions that can lead to arbitrary code execution. The attack vector operates entirely through the authentication interface, making it particularly dangerous as it can be exploited without requiring prior system access or elevated privileges.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass full system compromise capabilities. When successfully exploited, the buffer overflow allows attackers to execute arbitrary commands with the privileges of the affected service account, typically resulting in complete system takeover. The vulnerability affects systems running samba versions that incorporate the vulnerable PAM modules, making it particularly relevant in enterprise environments where samba-based authentication is prevalent. Organizations utilizing these authentication modules face significant risk as the attack can be conducted remotely without requiring physical access to the target system, aligning with ATT&CK technique T1110 for credential access and T1059 for command and script injection.
Mitigation strategies for CVE-2000-0843 require immediate implementation of software patches provided by samba developers, as the vulnerability represents an unpatched condition in affected versions. System administrators should prioritize updating their samba installations to versions that have addressed this specific buffer overflow issue in the PAM modules. Additional protective measures include implementing strict input validation controls at network boundaries, monitoring authentication logs for suspicious long user name attempts, and considering temporary disablement of the vulnerable PAM modules until proper patches are deployed. Network segmentation and access control policies should be strengthened to limit potential exploitation avenues, while regular security assessments should verify that all samba components have been properly updated to prevent similar vulnerabilities from persisting in the environment.