CVE-2024-39468 in Linux
Summary
by MITRE • 06/25/2024
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix deadlock in smb2_find_smb_tcon()
Unlock cifs_tcp_ses_lock before calling cifs_put_smb_ses() to avoid such deadlock.
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Analysis
by VulDB Data Team • 04/07/2026
The vulnerability identified as CVE-2024-39468 represents a critical deadlock condition within the Linux kernel's SMB client implementation that specifically affects the smb2_find_smb_tcon() function. This issue manifests in the context of Server Message Block protocol implementations where the kernel's SMB client subsystem encounters a synchronization problem during connection management operations. The flaw occurs when attempting to establish or maintain SMB network connections through the CIFS (Common Internet File System) protocol implementation that underlies SMB functionality in Linux environments.
The technical root cause of this vulnerability stems from improper lock management within the kernel's SMB client code where the cifs_tcp_ses_lock mutex is not released before invoking the cifs_put_smb_ses() cleanup function. This creates a classic deadlock scenario where the lock acquisition sequence becomes circular, preventing any further progress in the connection management code path. The function smb2_find_smb_tcon() is responsible for locating and establishing SMB tree connections, but it fails to properly sequence the lock release operation before performing the session cleanup, resulting in a situation where the same lock is held while attempting to acquire it again.
The operational impact of this vulnerability extends beyond simple functional failure to create complete system stall conditions that can affect network availability and system responsiveness. When the deadlock occurs, processes attempting to establish SMB connections or manage existing sessions become indefinitely blocked, leading to resource exhaustion and potential denial of service conditions for applications relying on SMB file access. This affects systems running Linux kernels with CIFS/SMB client implementations, particularly those in enterprise environments where SMB-based file sharing is prevalent. The vulnerability can be exploited by malicious actors to create persistent denial of service conditions or by legitimate users inadvertently triggering the deadlock through specific connection patterns.
Mitigation strategies for CVE-2024-39468 require immediate kernel updates to address the lock management issue in the SMB client subsystem. System administrators should prioritize patching their Linux distributions to obtain the fixed kernel version that properly releases the cifs_tcp_ses_lock before calling cifs_put_smb_ses(). The fix implements proper lock ordering by ensuring that mutex locks are released before cleanup operations are performed. Additionally, monitoring systems should be implemented to detect potential deadlock conditions in SMB connection management, and administrators should consider temporarily disabling SMB client functionality if immediate patching is not feasible. This vulnerability aligns with CWE-362, which describes concurrent execution using lock, and follows ATT&CK technique T1499.004 for denial of service through resource exhaustion, making it particularly concerning for enterprise security posture management.