CVE-2007-3843 in Linux
Summary
by MITRE
The Linux kernel before 2.6.23-rc1 checks the wrong global variable for the CIFS sec mount option, which might allow remote attackers to spoof CIFS network traffic that the client configured for security signatures, as demonstrated by lack of signing despite sec=ntlmv2i in a SetupAndX request.
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Analysis
by VulDB Data Team • 07/25/2019
The vulnerability described in CVE-2007-3843 represents a critical security flaw in the Linux kernel's implementation of the Common Internet File System protocol handling. This issue affects kernel versions prior to 2.6.23-rc1 and stems from a fundamental misimplementation in how the kernel processes the CIFS sec mount option. The flaw specifically involves the incorrect checking of global variables during the CIFS protocol negotiation process, creating a potential vector for man-in-the-middle attacks and credential interception.
The technical nature of this vulnerability lies in the kernel's failure to properly validate the security signature requirements when establishing CIFS connections. When users mount CIFS shares with the sec=ntlmv2i parameter, the system should enforce security signatures to protect against tampering and unauthorized access. However, due to the variable checking error, the kernel fails to properly implement these security measures, allowing attackers to bypass signature validation mechanisms. This misconfiguration enables remote adversaries to spoof network traffic and potentially intercept or modify data transmitted between the client and server.
The operational impact of this vulnerability extends beyond simple network monitoring capabilities, as it fundamentally undermines the security assurances that CIFS connections are designed to provide. Attackers can exploit this weakness to perform session hijacking, data corruption, or credential theft when connecting to CIFS shares configured with security signature requirements. The vulnerability is particularly concerning because it operates at the kernel level, meaning that successful exploitation can compromise the entire system's security posture rather than just individual applications. This flaw directly violates the principle of least privilege and can lead to unauthorized access to sensitive network resources.
The vulnerability aligns with CWE-284, which addresses improper access control in system components, and demonstrates how kernel-level implementation errors can create security gaps that persist across multiple network protocols. From an ATT&CK framework perspective, this vulnerability enables techniques such as credential access through network protocol manipulation and privilege escalation via kernel exploitation. Organizations using Linux systems for file sharing operations face significant risk if they have not updated to kernel versions 2.6.23-rc1 or later, as the vulnerability allows attackers to bypass security controls that are fundamental to protecting network resources. The recommended mitigation strategy involves immediate kernel updates to versions that properly implement the CIFS security signature validation, along with network monitoring to detect potential exploitation attempts. Additionally, system administrators should review their CIFS mount configurations and implement additional network security controls to minimize the attack surface while patches are deployed.