CVE-2024-26936 in Linux
Summary
by MITRE • 05/01/2024
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: validate request buffer size in smb2_allocate_rsp_buf()
The response buffer should be allocated in smb2_allocate_rsp_buf before validating request. But the fields in payload as well as smb2 header is used in smb2_allocate_rsp_buf(). This patch add simple buffer size validation to avoid potencial out-of-bounds in request buffer.
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Analysis
by VulDB Data Team • 01/26/2026
The vulnerability identified as CVE-2024-26936 resides within the Linux kernel's ksmbd implementation, which serves as a SMB/CIFS server component enabling file sharing over network protocols. This specific flaw manifests in the smb2_allocate_rsp_buf function where the buffer allocation process occurs before proper request validation, creating a potential security risk that could be exploited by malicious actors. The ksmbd subsystem operates under the broader SMB2 protocol implementation that governs how Windows and other systems communicate over network file shares, making it a critical component in enterprise network infrastructure.
The technical flaw stems from an improper sequence in buffer handling within the SMB2 response allocation routine. The function attempts to allocate response buffers before validating the size of the incoming request buffer, which creates a scenario where malformed or oversized request data could lead to memory corruption. The vulnerability specifically involves the use of fields from both the SMB2 header and the payload data within the smb2_allocate_rsp_buf function itself, meaning that the validation logic relies on potentially untrusted data before the buffer allocation has been properly secured. This violates fundamental security principles where input validation should occur before any resource allocation to prevent out-of-bounds memory access patterns.
The operational impact of this vulnerability extends beyond simple buffer overflow conditions, potentially allowing attackers to execute arbitrary code or cause denial of service within systems running affected kernel versions. When an attacker sends a specially crafted SMB2 request with oversized buffer parameters, the function's failure to validate request size before allocation could result in memory corruption that might be exploited to gain elevated privileges or disrupt service availability. This vulnerability affects systems that utilize the ksmbd module for SMB/CIFS file sharing operations, particularly those in enterprise environments where network file sharing is prevalent and where the kernel version has not been updated to include the patch. The potential for remote code execution makes this a critical vulnerability that requires immediate attention from system administrators and security teams.
Mitigation strategies should focus on immediate kernel updates that incorporate the patch addressing the buffer validation sequence issue in smb2_allocate_rsp_buf. Organizations should prioritize patch management processes to ensure all systems running affected kernel versions receive the security update. Additionally, network segmentation and firewall rules can be implemented to restrict SMB/CIFS traffic to trusted networks, reducing the attack surface. Monitoring for suspicious SMB2 traffic patterns and implementing intrusion detection systems can help identify potential exploitation attempts. The vulnerability aligns with CWE-129, which addresses improper validation of array index or buffer size, and may be categorized under ATT&CK technique T1059 for command and scripting interpreter usage as attackers might leverage this vulnerability to execute malicious code. Security teams should also consider implementing kernel hardening measures such as stack canaries and address space layout randomization to further protect against potential exploitation attempts.