CVE-2022-47940 in Linux
Summary
by MITRE • 12/23/2022
An issue was discovered in ksmbd in the Linux kernel before 5.18.18. fs/ksmbd/smb2pdu.c lacks length validation in the non-padding case in smb2_write.
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Analysis
by VulDB Data Team • 08/18/2025
The vulnerability identified as CVE-2022-47940 resides within the ksmbd subsystem of the Linux kernel, specifically affecting versions prior to 5.18.18. This issue manifests in the smb2pdu.c file where insufficient validation occurs during write operations, creating a potential avenue for exploitation that could compromise system integrity and availability. The ksmbd implementation serves as a kernel-space SMB/CIFS server that enables Linux systems to function as file servers supporting the SMB protocol commonly used in enterprise environments for file sharing and network access.
The technical flaw stems from the absence of proper length validation within the smb2_write function when processing non-padding cases in the SMB2 protocol implementation. This validation gap allows for malformed or excessively large write requests to be processed without adequate boundary checking, potentially leading to memory corruption or buffer overflow conditions. The vulnerability specifically affects how the system handles write operations in the SMB2 protocol where padding is not applied, creating a scenario where attacker-controlled data can manipulate memory layout and execution flow. This weakness aligns with CWE-129 Input Validation and CWE-787 Out-of-bounds Write, representing fundamental security flaws that can enable privilege escalation or denial of service conditions.
The operational impact of this vulnerability extends beyond simple memory corruption as it affects the core functionality of SMB file sharing services running on affected Linux systems. An attacker capable of establishing an SMB connection to a vulnerable system could potentially exploit this flaw to execute arbitrary code with kernel privileges, effectively compromising the entire system. The vulnerability's exploitation could result in complete system takeover, data exfiltration, or persistent backdoor installation, making it particularly dangerous in enterprise environments where SMB services are commonly deployed. Additionally, the impact extends to network availability as successful exploitation could lead to system crashes or forced reboots, creating denial of service conditions that disrupt legitimate business operations.
Mitigation strategies for CVE-2022-47940 primarily focus on applying the official kernel patch released with version 5.18.18 or later, which implements proper length validation in the smb2_write function. Organizations should prioritize updating their kernel versions across all systems running ksmbd services, particularly those serving as SMB file servers or participating in network file sharing environments. Network segmentation and access control measures should be implemented to limit exposure of vulnerable systems, while monitoring solutions should be deployed to detect unusual SMB traffic patterns that might indicate exploitation attempts. Security teams should also consider disabling SMB services when not required and implementing strict firewall rules to restrict SMB traffic to trusted network segments, aligning with ATT&CK technique T1071.004 Application Layer Protocol: SMB/Windows Admin Shares to prevent unauthorized access to vulnerable services.