CVE-2024-26954 in Linux
Summary
by MITRE • 05/01/2024
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix slab-out-of-bounds in smb_strndup_from_utf16()
If ->NameOffset of smb2_create_req is smaller than Buffer offset of smb2_create_req, slab-out-of-bounds read can happen from smb2_open. This patch set the minimum value of the name offset to the buffer offset to validate name length of smb2_create_req().
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Analysis
by VulDB Data Team • 01/26/2026
The vulnerability CVE-2024-26954 affects the Linux kernel's ksmbd implementation, specifically within the smb_strndup_from_utf16() function that handles SMB2 protocol operations. This issue resides in the kernel-based SMB daemon that provides SMB/CIFS file sharing capabilities to Linux systems. The flaw manifests when processing SMB2 create requests, where the kernel fails to properly validate the relationship between the NameOffset field and the buffer offset within the smb2_create_req structure. This improper validation creates a potential for out-of-bounds memory access that could be exploited by malicious actors.
The technical root cause of this vulnerability stems from inadequate input validation within the SMB2 protocol handling code. When the kernel processes an smb2_create_req packet, it examines the NameOffset field which specifies where the file name begins within the request buffer. However, the implementation does not ensure that NameOffset is properly positioned relative to the actual buffer boundaries. When NameOffset falls below the buffer offset, the smb_strndup_from_utf16() function attempts to read memory locations that extend beyond the allocated buffer boundaries, resulting in a slab-out-of-bounds read condition. This type of vulnerability falls under CWE-129 Input Validation and CWE-787 Out-of-bounds Read as identified by the Common Weakness Enumeration.
The operational impact of this vulnerability extends beyond simple memory corruption, as it represents a potential pathway for privilege escalation and system compromise. Attackers could leverage this out-of-bounds read to access sensitive kernel memory regions, potentially extracting confidential data or manipulating kernel structures. The vulnerability affects systems running Linux kernels with ksmbd support, particularly those serving SMB/CIFS shares to clients. Given that SMB is widely used for file sharing in enterprise environments, this vulnerability could be exploited in targeted attacks against networked systems. The ATT&CK framework categorizes this as a privilege escalation technique through kernel memory corruption, with potential for lateral movement once initial access is achieved.
The patch implemented to address this vulnerability enforces proper validation by setting a minimum value for the NameOffset field that ensures it cannot be smaller than the buffer offset. This approach prevents the out-of-bounds read condition by guaranteeing that name length validation occurs within legitimate buffer boundaries. The fix aligns with secure coding practices that emphasize input validation and boundary checking. System administrators should prioritize applying this patch to all affected Linux systems running ksmbd, particularly those serving SMB shares in production environments. The vulnerability demonstrates the critical importance of proper memory management in kernel modules and highlights the need for comprehensive input validation in network protocol implementations. Organizations should conduct vulnerability assessments to identify systems running affected kernel versions and implement proper monitoring for potential exploitation attempts targeting this specific out-of-bounds read condition.