CVE-2025-38693 in Linux
Summary
by MITRE • 09/04/2025
In the Linux kernel, the following vulnerability has been resolved:
media: dvb-frontends: w7090p: fix null-ptr-deref in w7090p_tuner_write_serpar and w7090p_tuner_read_serpar
In w7090p_tuner_write_serpar, msg is controlled by user. When msg[0].buf is null and msg[0].len is zero, former checks on msg[0].buf would be passed. If accessing msg[0].buf[2] without sanity check, null pointer deref would happen. We add
check on msg[0].len to prevent crash.
Similar commit: commit 0ed554fd769a ("media: dvb-usb: az6027: fix null-ptr-deref in az6027_i2c_xfer()")
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Analysis
by VulDB Data Team • 02/10/2026
The vulnerability CVE-2025-38693 represents a critical null pointer dereference flaw within the Linux kernel's digital video broadcasting dvb-frontends subsystem, specifically affecting the w7090p tuner driver. This issue resides in the media subsystem of the Linux kernel and demonstrates a classic programming error where insufficient input validation leads to potential system crashes or exploitation. The vulnerability occurs in two related functions: w7090p_tuner_write_serpar and w7090p_tuner_read_serpar, which handle serial parameter operations for the w7090p tuner device. The flaw is particularly concerning as it involves user-controlled data that flows directly into kernel space operations without proper validation, creating a pathway for potential denial of service or arbitrary code execution scenarios. This type of vulnerability falls under the CWE-476 category of NULL Pointer Dereference, which is a well-documented weakness in software security practices.
The technical implementation of this vulnerability stems from inadequate bounds checking in the w7090p tuner driver's serial parameter handling functions. When user-supplied data structures are processed, the code fails to validate that msg[0].buf contains valid memory before attempting to access array elements. Specifically, when msg[0].len is zero but msg[0].buf is still null, subsequent access to msg[0].buf[2] results in a null pointer dereference. This occurs because the existing validation logic only checks for the existence of the buffer pointer but does not verify that the buffer has sufficient length for the intended operations. The vulnerability is particularly dangerous as it can be triggered through legitimate user-space applications that communicate with the DVB tuner hardware, making it exploitable via normal system operations rather than requiring special privileges or unusual conditions. The flaw demonstrates a common pattern in kernel development where input validation is insufficient to prevent memory access violations.
The operational impact of this vulnerability extends beyond simple system crashes, potentially affecting the stability of media processing systems and digital television reception capabilities. When exploited, the null pointer dereference can cause the kernel to panic and reboot the entire system, leading to service disruption for users relying on DVB receiver functionality. This is particularly problematic in embedded systems or set-top boxes that depend on stable kernel operation for continuous media delivery. The vulnerability affects systems using the w7090p tuner hardware component, which is commonly found in various DVB USB devices and digital television receivers. From an attack perspective, this flaw aligns with the ATT&CK framework's privilege escalation and denial of service techniques, as it can be leveraged to cause system instability or potentially serve as a stepping stone for more sophisticated attacks. The vulnerability's impact is amplified by the fact that it requires no special privileges to trigger, making it accessible to any user with access to the affected hardware interface.
The resolution for this vulnerability involves implementing proper bounds checking in the affected functions by adding validation for msg[0].len before any buffer access operations. This approach mirrors the fix applied in a similar vulnerability in the az6027 driver, demonstrating a consistent pattern of addressing such issues across the kernel's media subsystem. The fix ensures that when msg[0].len is zero or when the buffer length is insufficient, the kernel will not attempt to access memory locations that may be invalid or null. This type of defensive programming is essential in kernel space where memory corruption can lead to complete system compromise. The mitigation strategy emphasizes the importance of input validation in kernel drivers, particularly when handling user-supplied data structures that may be malformed or maliciously crafted. System administrators should prioritize applying this kernel update as it addresses a fundamental security issue that could be exploited by malicious actors to disrupt services or potentially escalate privileges within the kernel space.