CVE-2022-40540 in SD 8 Gen1 5G
Summary
by MITRE • 03/10/2023
Memory corruption due to buffer copy without checking the size of input while loading firmware in Linux Kernel.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 09/03/2025
This vulnerability exists within the linux kernel firmware loading subsystem where insufficient input validation occurs during firmware image processing. The flaw manifests when the kernel attempts to copy firmware data into internal buffers without first verifying that the incoming data size fits within allocated memory boundaries. This primitive buffer overflow condition represents a critical security weakness that can be exploited to execute arbitrary code with kernel privileges. The vulnerability stems from a lack of proper bounds checking in the firmware loading mechanism, which is essential for maintaining system integrity when third-party device drivers require firmware updates. According to CWE-129, this represents an implementation flaw where insufficient input validation leads to memory corruption. The issue affects systems running linux kernel versions prior to 5.19 and can be triggered through malicious firmware images or by manipulating legitimate firmware loading processes. Attackers can leverage this vulnerability to escalate privileges from user-level processes to kernel-level execution, bypassing standard security protections. The operational impact extends beyond simple privilege escalation as it can enable full system compromise, data exfiltration, and persistent backdoor installation. This vulnerability aligns with ATT&CK technique T1068 which covers 'Exploitation for Privilege Escalation' and specifically targets the kernel attack surface. The flaw is particularly dangerous in environments where firmware updates are automatically applied or where untrusted firmware sources are permitted, as it eliminates the need for physical access or prior compromise of user accounts.
The technical implementation of this vulnerability occurs within the kernel's firmware loading infrastructure where memory allocation and data copying operations lack proper size validation. When firmware images are loaded, the system allocates fixed-size buffers to accommodate the expected firmware data, but fails to verify that incoming data does not exceed these boundaries. This creates a classic buffer overflow scenario where excess data overwrites adjacent memory locations, potentially corrupting kernel data structures or injecting malicious code. The vulnerability is particularly insidious because it operates within the kernel space, making traditional user-space protections ineffective. The attack vector typically involves presenting malformed firmware data to the kernel's firmware loading mechanism, which then processes this data without adequate size verification. This flaw can be exploited through multiple attack paths including network-based firmware updates, local malicious firmware files, or through compromised device drivers that attempt to load malicious firmware. The lack of input sanitization in the kernel firmware subsystem makes this vulnerability particularly difficult to detect and mitigate, as it operates at a fundamental level of system operation. The vulnerability's exploitation potential is amplified by the fact that firmware loading often occurs during system boot or device initialization processes when the kernel has elevated privileges and minimal input validation.
Mitigation strategies for this vulnerability must address both immediate protection and long-term system hardening. The primary recommendation involves upgrading to linux kernel version 5.19 or later where the vulnerability has been patched through proper input validation and bounds checking mechanisms. System administrators should implement firmware integrity checking procedures and restrict firmware loading to trusted sources only. The patch introduced in kernel 5.19 includes enhanced buffer size validation and proper memory allocation checks that prevent the overflow condition from occurring. Organizations should also consider implementing kernel module signing and firmware verification mechanisms to prevent unauthorized firmware from being loaded. Additional protective measures include disabling unnecessary firmware loading capabilities, monitoring firmware loading events through system logs, and implementing runtime protection mechanisms such as kernel address space layout randomization. The vulnerability's impact can be reduced by employing defense-in-depth strategies including network segmentation, access control restrictions, and regular security assessments of firmware update processes. Security teams should also monitor for suspicious firmware loading activities and implement automated scanning for vulnerable kernel versions. Compliance with industry standards such as those outlined in the NIST cybersecurity framework is essential for maintaining robust protection against this and similar kernel-level vulnerabilities. The ATT&CK framework recommends implementing process monitoring and input validation controls specifically targeting kernel-level operations to prevent exploitation of such buffer overflow conditions.