CVE-2014-3560 in Samba
Summary
by MITRE
NetBIOS name services daemon (nmbd) in Samba 4.0.x before 4.0.21 and 4.1.x before 4.1.11 allows remote attackers to execute arbitrary code via unspecified vectors that modify heap memory, involving a sizeof operation on an incorrect variable in the unstrcpy macro in string_wrappers.h.
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Analysis
by VulDB Data Team • 02/10/2022
The vulnerability identified as CVE-2014-3560 represents a critical heap-based buffer overflow in the NetBIOS name services daemon component of Samba software. This flaw exists within the nmbd service which handles NetBIOS name service operations and is part of the broader Samba suite used for file and print sharing between Unix and Windows systems. The vulnerability affects Samba versions 4.0.x prior to 4.0.21 and 4.1.x prior to 4.1.11, making it a significant concern for organizations maintaining legacy Samba installations. The issue manifests through improper memory management during string operations, specifically within the string_wrappers.h header file where the unstrcpy macro executes an incorrect sizeof operation on a variable that leads to memory corruption.
The technical root cause of this vulnerability stems from a flawed implementation in the string handling macros within Samba's source code. When processing network requests containing specially crafted NetBIOS names, the unstrcpy macro performs a sizeof operation on an incorrect variable, leading to an improper calculation of buffer sizes. This incorrect sizing allows attackers to overwrite adjacent heap memory locations, potentially enabling arbitrary code execution. The vulnerability is classified as a heap overflow according to CWE-122, which describes improper restriction of operations within the bounds of a memory buffer. The flaw is particularly dangerous because it operates within the nmbd daemon process that typically runs with elevated privileges, providing attackers with potential escalation opportunities.
From an operational perspective, this vulnerability creates a severe attack surface for remote exploitation, as the nmbd service listens on standard NetBIOS ports and accepts connections from any network host. Attackers can leverage this vulnerability by sending maliciously crafted NetBIOS name requests that trigger the flawed string handling code path. The impact extends beyond simple code execution to potentially allow full system compromise, especially when the vulnerable Samba server is accessible from untrusted networks. The vulnerability affects systems running Samba in various configurations including file servers, domain controllers, and print servers that rely on NetBIOS name resolution services. Organizations with exposed Samba services face significant risk of unauthorized access, data exfiltration, and persistent backdoor establishment.
The mitigation strategy for CVE-2014-3560 requires immediate patching of affected Samba installations to versions 4.0.21 or 4.1.11 and later. Organizations should also implement network segmentation to restrict access to Samba services, particularly the nmbd daemon, by limiting exposure to trusted networks only. Additional defensive measures include disabling unnecessary NetBIOS name service functionality when not required, monitoring network traffic for suspicious NetBIOS name requests, and implementing intrusion detection systems to identify exploitation attempts. According to ATT&CK framework, this vulnerability maps to T1059.007 for remote code execution and T1068 for local privilege escalation, making it a critical target for both network-based and host-based security controls. System administrators should also consider implementing application whitelisting policies to prevent unauthorized execution of vulnerable Samba components and conduct regular vulnerability assessments to identify other potential heap-based buffer overflow issues in network services.