CVE-2016-2111 in Samba
Summary
by MITRE
The NETLOGON service in Samba 3.x and 4.x before 4.2.11, 4.3.x before 4.3.8, and 4.4.x before 4.4.2, when a domain controller is configured, allows remote attackers to spoof the computer name of a secure channel's endpoint, and obtain sensitive session information, by running a crafted application and leveraging the ability to sniff network traffic, a related issue to CVE-2015-0005.
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Analysis
by VulDB Data Team • 07/24/2022
The vulnerability described in CVE-2016-2111 represents a critical security flaw in the Samba implementation of the NETLOGON protocol, affecting versions 3.x and 4.x prior to specific patch releases. This weakness resides within the domain controller configuration where the NETLOGON service handles secure channel communications between domain controllers and member servers. The vulnerability stems from insufficient validation of computer names during the secure channel establishment process, creating an opportunity for remote attackers to manipulate the authentication flow. The flaw specifically targets the secure channel endpoint identification mechanism, allowing malicious actors to spoof computer names and potentially compromise the integrity of domain communications. This issue operates under the broader category of authentication bypass vulnerabilities and falls within the CWE-287 category of improper authentication, which is a fundamental weakness in network security protocols.
The technical exploitation of CVE-2016-2111 requires an attacker to have network access to the target domain and the ability to intercept network traffic, which aligns with the ATT&CK technique T1071.004 for application layer protocol usage. The vulnerability enables attackers to perform man-in-the-middle attacks by spoofing computer names during secure channel establishment, effectively allowing them to impersonate legitimate domain controller endpoints. This manipulation can lead to the extraction of sensitive session information, including authentication tokens and session keys that are crucial for maintaining domain security. The attack vector leverages the ability to sniff network traffic, making it particularly dangerous in environments where network monitoring is insufficient or where attackers can establish network positions to capture relevant communications. The vulnerability creates a pathway for privilege escalation and lateral movement within the domain, as successful exploitation can provide attackers with elevated privileges and access to critical domain resources.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally undermines the security model of Windows domain environments that rely on Samba for cross-platform compatibility. Organizations using affected Samba versions face significant risks including unauthorized access to domain resources, potential credential theft, and the possibility of establishing persistent access within their network infrastructure. The vulnerability's relationship to CVE-2015-0005 demonstrates a pattern of weaknesses in the NETLOGON protocol implementation, suggesting that multiple related vulnerabilities may exist within the same security framework. This type of flaw can enable attackers to perform advanced persistent threat operations, as the ability to spoof secure channel endpoints can be used to establish backdoors or maintain access to domain resources without detection. The impact is particularly severe in enterprise environments where domain controllers serve as critical infrastructure components for authentication and authorization services, making this vulnerability a prime target for attackers seeking to compromise entire domain networks.
Organizations should immediately implement mitigations including updating to patched versions of Samba that address the computer name validation issues in the NETLOGON service. The recommended approach involves upgrading to Samba versions 4.2.11, 4.3.8, or 4.4.2 respectively, which contain fixes for the spoofing vulnerability. Network segmentation and monitoring should be enhanced to detect anomalous secure channel establishment attempts, while implementing network access controls to limit the ability of unauthorized parties to intercept traffic. Security controls should include monitoring for unusual computer name changes in domain controller communications, as well as implementing network intrusion detection systems that can identify potential exploitation attempts. The vulnerability also highlights the importance of maintaining up-to-date security patches across all domain controller implementations, as the attack requires minimal privileges to execute and can be particularly difficult to detect once established. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of affected Samba versions within the organization's infrastructure.