CVE-2016-2113 in Samba
Summary
by MITRE
Samba 4.x before 4.2.11, 4.3.x before 4.3.8, and 4.4.x before 4.4.2 does not verify X.509 certificates from TLS servers, which allows man-in-the-middle attackers to spoof LDAPS and HTTPS servers and obtain sensitive information via a crafted certificate.
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Analysis
by VulDB Data Team • 07/24/2022
The vulnerability identified as CVE-2016-2113 represents a critical security flaw in Samba implementations across multiple version ranges including 4.x before 4.2.11, 4.3.x before 4.3.8, and 4.4.x before 4.4.2. This issue fundamentally undermines the cryptographic security mechanisms that Samba employs to establish secure communications with LDAP Directory Services and HTTPS servers. The vulnerability specifically targets the X.509 certificate verification process within the Transport Layer Security implementation, creating a pathway for malicious actors to conduct man-in-the-middle attacks against Samba services.
The technical flaw manifests in the absence of proper certificate validation procedures when Samba establishes TLS connections to remote servers. When Samba attempts to connect to LDAPS (LDAP over SSL) or HTTPS services, it fails to perform the essential X.509 certificate verification steps that should confirm the authenticity and trustworthiness of the remote server's certificate. This omission allows attackers to present forged certificates that appear legitimate to Samba's connection process, enabling them to intercept and manipulate communications between Samba clients and target servers. The vulnerability essentially disables the certificate pinning and validation mechanisms that are fundamental to TLS security protocols.
The operational impact of this vulnerability extends far beyond simple data interception, as it enables attackers to gain unauthorized access to sensitive information and potentially compromise entire network infrastructures. When Samba services connect to LDAPS servers for authentication or directory queries, attackers can seamlessly intercept these communications and obtain user credentials, directory information, and other confidential data. The implications are particularly severe for organizations relying on Samba for file sharing and authentication services, as compromised connections can lead to complete system compromise. This vulnerability directly aligns with CWE-295 which addresses improper certificate validation and represents a significant weakness in the security architecture of affected Samba implementations.
Organizations utilizing affected Samba versions face substantial risk of credential theft, data exfiltration, and unauthorized system access. The vulnerability creates an attack surface that allows adversaries to establish persistent access points within networks where Samba services are deployed. Attackers can leverage this weakness to perform reconnaissance activities, escalate privileges, and move laterally within compromised environments. The impact is particularly concerning given Samba's widespread deployment in enterprise environments and its role in critical authentication and file sharing services. This vulnerability also maps to ATT&CK technique T1046 which describes the use of network service scanning to identify and exploit weak TLS implementations, and T1552 which covers the compromise of credentials through man-in-the-middle attacks.
The recommended mitigation strategy involves immediate patching of affected Samba installations to versions that properly implement X.509 certificate verification. Organizations should prioritize upgrading to Samba 4.2.11, 4.3.8, or 4.4.2 respectively, depending on their current version. Additionally, network administrators should implement monitoring solutions to detect anomalous certificate behaviors and establish certificate pinning policies where possible. Security teams should conduct comprehensive vulnerability assessments to identify all Samba installations within their environments and ensure proper TLS configuration. The remediation process should also include verifying that certificate validation is properly configured in all Samba service configurations and implementing network-level controls to prevent unauthorized certificate issuance within the organization's infrastructure.