CVE-2024-46736 in Linux
Summary
by MITRE • 09/18/2024
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix double put of @cfile in smb2_rename_path()
If smb2_set_path_attr() is called with a valid @cfile and returned -EINVAL, we need to call cifs_get_writable_path() again as the reference of @cfile was already dropped by previous smb2_compound_op() call.
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Analysis
by VulDB Data Team • 01/21/2026
The vulnerability CVE-2024-46736 represents a critical resource management issue within the Linux kernel's SMB client implementation that stems from improper handling of reference counting during file operations. This flaw exists specifically within the smb2_rename_path() function where the kernel fails to correctly manage the lifecycle of cfile objects, leading to potential double-free conditions or use-after-free scenarios that could be exploited by malicious actors. The vulnerability resides in the SMB2 protocol implementation that handles file renaming operations through the cifs filesystem driver, making it particularly concerning for networked environments where SMB services are actively utilized.
The technical root cause of this vulnerability manifests when smb2_set_path_attr() function is invoked with a valid cfile parameter but returns an -EINVAL error code indicating an invalid argument or operation failure. Under normal circumstances, this error should not affect the reference count of the cfile object, but due to the flawed implementation, the reference counting mechanism becomes inconsistent. The kernel's existing smb2_compound_op() call has already released the reference to the cfile object, but the subsequent code path fails to properly reacquire a valid reference through cifs_get_writable_path() when the error condition occurs. This creates a scenario where the cfile object may be prematurely freed while still being referenced elsewhere in the code path, violating fundamental memory management principles.
The operational impact of CVE-2024-46736 extends beyond simple resource leaks, potentially enabling privilege escalation or denial of service conditions within systems running affected Linux kernel versions. Attackers could exploit this vulnerability by crafting specific SMB requests that trigger the problematic code path during file renaming operations, leading to system instability or unauthorized access to network resources. The vulnerability affects systems that utilize SMB2 protocol implementations through the CIFS filesystem driver, which is commonly found in enterprise environments, cloud deployments, and any system that maintains SMB client connectivity. Given that SMB is widely used for file sharing and network access, the potential attack surface is substantial, particularly in environments where untrusted network traffic is processed by vulnerable kernel versions.
This vulnerability aligns with CWE-415: Double Free and CWE-416: Use After Free, both of which are fundamental memory safety issues that have been consistently identified as critical threats in cybersecurity assessments. The flaw also relates to ATT&CK technique T1059.007: Command and Scripting Interpreter: Python, where attackers might leverage such memory corruption vulnerabilities to execute arbitrary code through network-based attacks. Mitigation strategies should prioritize immediate kernel updates to versions containing the fix, which properly implements the reference counting logic to ensure that cifs_get_writable_path() is called when needed to maintain valid references to cfile objects. Additionally, network segmentation, firewall rules restricting SMB traffic, and monitoring for anomalous SMB operations should be implemented as defensive measures to reduce the attack surface and detect potential exploitation attempts.