CVE-2017-12151 in Samba
Summary
by MITRE
A flaw was found in the way samba client before samba 4.4.16, samba 4.5.14 and samba 4.6.8 used encryption with the max protocol set as SMB3. The connection could lose the requirement for signing and encrypting to any DFS redirects, allowing an attacker to read or alter the contents of the connection via a man-in-the-middle attack.
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Analysis
by VulDB Data Team • 12/30/2022
The vulnerability identified as CVE-2017-12151 represents a critical security flaw in samba client implementations that affected versions prior to samba 4.4.16, 4.5.14, and 4.6.8. This issue specifically manifests when the samba client operates with the maximum protocol set to SMB3, creating a significant weakness in the authentication and encryption mechanisms that are fundamental to secure network communications. The flaw stems from improper handling of security requirements during DFS (Distributed File System) redirect operations, where the client fails to maintain the necessary security policies that should be enforced throughout the entire communication session.
The technical nature of this vulnerability lies in the samba client's failure to enforce mandatory security parameters when processing DFS redirects. Normally, when SMB3 protocol is used, connections should maintain strict requirements for both message signing and encryption to prevent unauthorized access and data tampering. However, this flaw allows the security context to be weakened or lost during the redirect process, effectively creating a gap where attackers can exploit the connection. The vulnerability operates at the protocol level, specifically targeting the session management and security negotiation mechanisms within samba's SMB implementation, making it particularly dangerous for environments that rely heavily on DFS services.
The operational impact of CVE-2017-12151 is severe and far-reaching for organizations using affected samba client versions. An attacker positioned in a man-in-the-middle position can exploit this weakness to intercept and manipulate network traffic between the client and server, potentially gaining access to sensitive data or modifying file contents without detection. This vulnerability directly violates the core security principles of confidentiality, integrity, and availability that network protocols are designed to protect. The risk is particularly elevated in enterprise environments where DFS services are commonly deployed for file sharing and distributed computing, as these scenarios create multiple potential attack vectors through which the flaw can be exploited.
Organizations should prioritize immediate patching of all affected samba client installations to address this vulnerability. The mitigation strategy involves upgrading to the patched versions of samba that contain the necessary security fixes to properly maintain encryption and signing requirements during DFS redirect operations. Additionally, network administrators should implement monitoring solutions to detect unusual traffic patterns that might indicate exploitation attempts. This vulnerability aligns with CWE-310, which addresses cryptographic weaknesses, and maps to ATT&CK technique T1046 for network service scanning and T1071 for application layer protocol usage, as attackers may leverage this flaw to establish persistent access through compromised file sharing services.
The broader implications of this vulnerability extend beyond immediate exploitation risks to highlight the importance of proper security protocol enforcement in network implementations. This flaw demonstrates how seemingly minor protocol handling issues can create significant security gaps that undermine the entire security architecture of networked systems. Organizations should conduct comprehensive security assessments of their samba implementations and review all DFS configurations to ensure proper security policies are maintained throughout all connection states. The vulnerability also underscores the necessity of maintaining current security patches and implementing robust network monitoring to detect and respond to exploitation attempts before they can cause substantial damage to organizational data integrity and confidentiality.