CVE-2023-3961 in Samba
Summary
by MITRE • 11/03/2023
A path traversal vulnerability was identified in Samba when processing client pipe names connecting to Unix domain sockets within a private directory. Samba typically uses this mechanism to connect SMB clients to remote procedure call (RPC) services like SAMR LSA or SPOOLSS, which Samba initiates on demand. However, due to inadequate sanitization of incoming client pipe names, allowing a client to send a pipe name containing Unix directory traversal characters (../). This could result in SMB clients connecting as root to Unix domain sockets outside the private directory. If an attacker or client managed to send a pipe name resolving to an external service using an existing Unix domain socket, it could potentially lead to unauthorized access to the service and consequential adverse events, including compromise or service crashes.
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Analysis
by VulDB Data Team • 08/30/2025
The vulnerability described in CVE-2023-3961 represents a critical path traversal flaw within the Samba file sharing implementation that specifically affects how the software handles client pipe names when establishing connections to Unix domain sockets. This vulnerability exists in the context of Samba's remote procedure call mechanism where clients connect to various services such as SAMR LSA and SPOOLSS through Unix domain sockets that are typically confined to a private directory structure. The fundamental issue lies in the insufficient validation of pipe names received from clients, which allows malicious actors to exploit directory traversal sequences that can bypass intended access controls and escape the designated private directory boundaries. The vulnerability is particularly concerning because it operates at the core of Samba's security model where Unix domain socket connections are used to facilitate secure communication between SMB clients and backend services, making it a potential gateway for privilege escalation attacks.
The technical exploitation of this vulnerability occurs when a malicious client crafts a pipe name containing directory traversal sequences such as "../" that are then processed by Samba without proper sanitization. This flaw enables attackers to manipulate the path resolution mechanism and potentially connect to Unix domain sockets located outside the intended private directory, including system-level services that are typically restricted to root access. The path traversal mechanism allows for arbitrary file access patterns that can bypass normal access controls, effectively enabling a client to establish connections to services that should remain protected within the private directory structure. This vulnerability is classified under CWE-22 as "Path Traversal" and represents a direct violation of the principle of least privilege in system security architecture, where access controls are meant to prevent unauthorized access to system resources. The flaw essentially allows for a form of privilege escalation where a client connection that should be restricted to a specific namespace can be manipulated to access broader system resources.
The operational impact of CVE-2023-3961 extends beyond simple unauthorized access to potentially include complete system compromise and service disruption. When an attacker successfully exploits this vulnerability, they can potentially connect to Unix domain sockets that provide access to critical system services such as authentication mechanisms, service management interfaces, or other privileged operations. The potential for service crashes exists when maliciously crafted pipe names cause the system to attempt connections to non-existent or system-critical resources, leading to denial of service conditions. Additionally, the vulnerability can be leveraged to gain unauthorized access to sensitive system information and potentially execute arbitrary code with elevated privileges. This vulnerability aligns with ATT&CK technique T1078 which covers Valid Accounts and privilege escalation techniques, as it enables attackers to bypass normal authentication mechanisms through manipulation of the Unix domain socket connection process.
Mitigation strategies for this vulnerability should focus on implementing strict input validation and sanitization of pipe names received from clients, ensuring that all path traversal sequences are properly detected and rejected. System administrators should consider implementing network segmentation and access controls to limit exposure of Samba services to untrusted networks, while also applying the latest security patches from Samba maintainers as soon as they become available. The implementation of additional monitoring and logging mechanisms around Unix domain socket connections can help detect anomalous access patterns that may indicate exploitation attempts. Organizations should also consider implementing principle of least privilege configurations where Samba services operate with minimal required privileges and where the private directory structure is properly secured with appropriate file permissions. The vulnerability highlights the importance of secure coding practices in network services and demonstrates how seemingly simple input validation flaws can result in significant security implications, particularly in systems that handle privileged operations through Unix domain sockets. Regular security audits and penetration testing should be conducted to identify similar path traversal vulnerabilities in other network services that may be exposed to similar attack vectors.