CVE-2025-38694 in Linux
Summary
by MITRE • 09/04/2025
In the Linux kernel, the following vulnerability has been resolved:
media: dvb-frontends: dib7090p: fix null-ptr-deref in dib7090p_rw_on_apb()
In dib7090p_rw_on_apb, 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 issue occurs when access
msg[1].buf[0] and msg[1].buf[1].
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-2025-38694 resides within the Linux kernel's digital video broadcast dvb-frontends subsystem, specifically affecting the dib7090p driver implementation. This issue represents a critical null pointer dereference condition that can lead to system crashes and potential denial of service scenarios. The vulnerability manifests in the dib7090p_rw_on_apb function where user-controlled data structures are processed without adequate validation, creating an exploitable path for malicious actors to disrupt system operations.
The technical flaw occurs when processing I2C transfer messages through the dib7090p driver interface. The msg parameter contains user-supplied data structures where msg[0].buf can be null while msg[0].len remains zero. The existing validation logic fails to properly check the length field before attempting to access memory locations within the buffer, specifically msg[0].buf[2] and msg[1].buf[0] and msg[1].buf[1]. This oversight creates a classic null pointer dereference scenario where the kernel attempts to access memory at address zero, resulting in immediate system termination. The vulnerability follows a pattern consistent with common software flaws identified in the CWE database under CWE-476, which specifically addresses null pointer dereference conditions.
The operational impact of this vulnerability extends beyond simple system crashes as it affects the entire DVB (Digital Video Broadcasting) frontend subsystem within Linux kernel environments. Systems utilizing DVB receivers, satellite tuners, or digital television hardware that employs the dib7090p driver are at risk of experiencing unexpected service interruptions. The vulnerability can be triggered through legitimate user-space applications that communicate with the kernel driver via standard I2C interfaces, making it particularly concerning for embedded systems, set-top boxes, and digital television receivers. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 (Resource Hijacking) and T1566.002 (Phishing with Social Engineering) as it can be leveraged to disrupt services and potentially create conditions for more sophisticated attacks.
Mitigation strategies for this vulnerability require immediate kernel updates that implement the necessary validation checks. The fix involves adding explicit length validation before buffer access operations, ensuring that msg[0].len and msg[1].len are properly checked before accessing their respective buffer contents. The solution follows a pattern established in a similar fix for the az6027 driver, demonstrating the importance of consistent security practices across kernel subsystems. System administrators should prioritize patching affected kernels, particularly in production environments where DVB frontend functionality is critical. Additionally, monitoring for unusual I2C communication patterns and implementing proper input validation at the application level can provide additional defense-in-depth measures against exploitation attempts.