CVE-2017-14746 in Samba
Summary
by MITRE
Use-after-free vulnerability in Samba 4.x before 4.7.3 allows remote attackers to execute arbitrary code via a crafted SMB1 request.
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Analysis
by VulDB Data Team • 12/09/2019
The vulnerability identified as CVE-2017-14746 represents a critical use-after-free flaw within the Samba implementation that affects versions prior to 4.7.3. This security defect manifests specifically within the SMB1 protocol handling mechanism, creating a pathway for remote attackers to potentially execute arbitrary code on affected systems. The vulnerability stems from improper memory management practices where freed memory locations are accessed after being deallocated, a classic pattern that can lead to unpredictable behavior and potential code execution. The Samba project, which provides file and print services for Windows networks on Unix-like systems, was particularly susceptible due to its widespread deployment in enterprise environments where SMB1 protocol support remained enabled.
The technical exploitation of this vulnerability occurs through carefully crafted SMB1 requests that trigger the use-after-free condition during the processing of specific protocol messages. When a malicious actor sends a specially constructed SMB1 packet, the Samba server's memory management routines fail to properly validate the state of allocated memory regions, allowing the attacker to manipulate freed memory pointers. This memory corruption can be leveraged to overwrite critical function pointers or execute shellcode within the context of the Samba service process. The vulnerability is particularly dangerous because it operates at the protocol level, requiring no authentication or local access to exploit, making it a prime target for automated attacks across networks. According to CWE classification, this vulnerability maps to CWE-416 which specifically addresses the use of freed memory conditions, while the ATT&CK framework would categorize this under T1210 - Exploitation of Remote Services and T1059 - Command and Scripting Interpreter as part of the broader attack chain.
The operational impact of CVE-2017-14746 extends beyond simple code execution, as successful exploitation can lead to complete system compromise and persistence within network environments. Organizations running vulnerable Samba versions face significant risk since SMB1 protocol support is often enabled by default in many installations, creating a broad attack surface. The vulnerability can be exploited across various operating systems that implement Samba, including Linux distributions and Unix-like systems where Samba serves as a primary file sharing solution. Network administrators must consider the potential for lateral movement within compromised environments, as attackers who gain initial access through this vulnerability can leverage the compromised Samba service to access additional network resources. The attack vector is particularly concerning because it operates over standard network ports, making it difficult to distinguish from legitimate traffic and potentially evading traditional network monitoring solutions that do not specifically target memory corruption vulnerabilities.
Mitigation strategies for CVE-2017-14746 primarily focus on immediate patching of affected Samba installations to version 4.7.3 or later, which contains the necessary memory management fixes. System administrators should also disable SMB1 protocol support on all affected servers, as this protocol is considered legacy and insecure by modern security standards. Network segmentation and firewall rules can be implemented to restrict SMB traffic to only necessary endpoints, reducing the attack surface. Additionally, monitoring for unusual SMB1 traffic patterns and implementing intrusion detection systems that can identify potential exploitation attempts provides defense-in-depth. Organizations should conduct comprehensive vulnerability assessments to identify all systems running vulnerable Samba versions and prioritize remediation efforts based on risk exposure. The implementation of automated patch management solutions helps ensure timely deployment of security updates across enterprise environments. Security teams must also consider the broader implications of this vulnerability within their overall security posture, as it highlights potential gaps in memory safety practices that could affect other components of the system infrastructure.