CVE-2014-7145 in Linux
Summary
by MITRE • 01/25/2023
The SMB2_tcon function in fs/cifs/smb2pdu.c in the Linux kernel before 3.16.3 allows remote CIFS servers to cause a denial of service (NULL pointer dereference and client system crash) or possibly have unspecified other impact by deleting the IPC$ share during resolution of DFS referrals.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2014-7145 represents a critical flaw in the Linux kernel's implementation of the Server Message Block protocol version 2 which affects systems running kernel versions prior to 3.16.3. This issue specifically targets the SMB2_tcon function located in the fs/cifs/smb2pdu.c file, demonstrating a classic null pointer dereference condition that can be exploited by remote CIFS servers to disrupt system operations. The vulnerability manifests when remote servers manipulate the IPC$ share during the resolution process of DFS (Distributed File System) referrals, creating a scenario where the kernel's handling of these dynamic references becomes compromised.
The technical exploitation of this vulnerability occurs through a carefully orchestrated sequence where a malicious CIFS server removes or modifies the IPC$ share while the Linux client system is in the process of resolving DFS referrals. This timing attack creates a race condition where the kernel attempts to access a null pointer that was previously valid but has since been invalidated by the remote server's actions. The underlying flaw stems from inadequate validation and error handling within the SMB2 protocol implementation, particularly in how the kernel manages the lifecycle of share references during dynamic resolution processes. This weakness directly maps to CWE-476 which identifies NULL pointer dereference as a fundamental programming error that can lead to system instability and potential privilege escalation scenarios.
The operational impact of this vulnerability extends beyond simple denial of service to potentially encompass more severe consequences including system crashes that can result in complete system downtime. When the kernel encounters the null pointer dereference, it typically triggers a kernel oops or panic condition that forces the system to reboot or becomes unresponsive to further operations. In environments where CIFS clients are extensively used for file sharing and network access, this vulnerability can create cascading failures that affect multiple users and services simultaneously. The remote nature of the attack means that an attacker does not require local system access or credentials to exploit this vulnerability, making it particularly dangerous in networked environments where systems may be exposed to untrusted CIFS servers.
Organizations affected by this vulnerability should implement immediate mitigations including kernel updates to version 3.16.3 or later, which contain the necessary patches to address the null pointer dereference condition. System administrators should also consider implementing network segmentation to limit exposure to untrusted CIFS servers and monitor for unusual network activity that might indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under the T1059.007 technique for exploitation of remote services, while the patching process aligns with the defensive technique of T1547.001 maintaining system integrity through software updates. Additional mitigations include configuring firewalls to restrict CIFS traffic to trusted networks and implementing intrusion detection systems that can identify suspicious DFS referral resolution patterns. The vulnerability demonstrates the importance of robust input validation and proper error handling in kernel space code, particularly when dealing with dynamic network protocols that involve shared state management between client and server components.