CVE-2025-38629 in Linux
Summary
by MITRE • 08/22/2025
In the Linux kernel, the following vulnerability has been resolved:
ALSA: usb: scarlett2: Fix missing NULL check
scarlett2_input_select_ctl_info() sets up the string arrays allocated via kasprintf(), but it misses NULL checks, which may lead to NULL dereference Oops. Let's add the proper NULL check.
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Analysis
by VulDB Data Team • 05/28/2026
The vulnerability identified as CVE-2025-38629 represents a critical null pointer dereference issue within the Linux kernel's Advanced Linux Sound Architecture subsystem, specifically affecting the scarlett2 USB audio device driver. This flaw resides in the usb_scarlett2 module which manages audio interfaces for Focusrite Scarlett 2nd generation USB audio devices. The vulnerability stems from inadequate input validation within the scarlett2_input_select_ctl_info() function, which is responsible for configuring control information for audio input selection. When this function allocates memory using kasprintf() for string arrays, it fails to verify whether the allocation succeeded, creating a scenario where subsequent operations attempt to dereference a null pointer, resulting in kernel oops and potential system instability.
The technical implementation of this vulnerability involves the scarlett2_input_select_ctl_info() function in the ALSA USB driver component, which operates under the Linux kernel's sound subsystem framework. According to CWE-476, this represents a NULL pointer dereference vulnerability that occurs when a pointer expected to contain a valid memory address instead contains NULL. The flaw specifically manifests when the function calls kasprintf() to dynamically allocate memory for string array elements but does not validate the return value before proceeding with operations that assume valid memory allocation. This pattern violates standard kernel programming practices and security guidelines that mandate proper error checking for all memory allocation operations. The vulnerability falls under the ATT&CK technique T1068, which involves the exploitation of legitimate credentials and system privileges to execute malicious code, as kernel-level null pointer dereferences can potentially be leveraged for privilege escalation or system compromise.
The operational impact of this vulnerability extends beyond simple system crashes, as kernel oops conditions can lead to complete system hangs or unexpected reboots, particularly in environments where audio services are critical for operations. The scarlett2 USB audio driver is commonly used in professional audio applications, digital audio workstations, and multimedia production environments where system stability is paramount. When exploited, this vulnerability can cause denial of service conditions that may disrupt audio processing workflows, potentially leading to data loss or production delays. The vulnerability affects systems running Linux kernel versions that include the scarlett2 USB audio driver implementation, particularly those supporting Focusrite Scarlett 2nd generation audio interfaces. Security researchers have noted that such kernel-level vulnerabilities are especially dangerous because they operate at the highest privilege level, making them attractive targets for attackers seeking to establish persistent access or escalate privileges within affected systems.
Mitigation strategies for CVE-2025-38629 primarily involve applying the official kernel patch that introduces proper NULL pointer validation after memory allocation. System administrators should prioritize updating to kernel versions that contain the fix, typically found in kernel releases following the patch implementation. The recommended approach involves implementing a comprehensive patch management program that includes regular kernel updates and security assessments. Organizations should also consider monitoring kernel logs for oops messages that may indicate exploitation attempts or system instability related to the scarlett2 driver. Additional protective measures include implementing kernel lockdown mechanisms, disabling unnecessary USB audio drivers when not required, and maintaining robust backup and recovery procedures. The vulnerability demonstrates the importance of adhering to secure coding practices in kernel development, particularly emphasizing the need for comprehensive error handling and input validation. Security teams should also consider implementing intrusion detection systems that monitor for unusual kernel behavior patterns that might indicate exploitation attempts. Regular security audits of kernel modules and driver implementations should be conducted to identify similar null pointer dereference vulnerabilities that may exist in other components of the Linux sound subsystem or USB driver framework.