CVE-2025-39714 in Linux
Summary
by MITRE • 09/05/2025
In the Linux kernel, the following vulnerability has been resolved:
media: usbtv: Lock resolution while streaming
When an program is streaming (ffplay) and another program (qv4l2) changes the TV standard from NTSC to PAL, the kernel crashes due to trying to copy to unmapped memory.
Changing from NTSC to PAL increases the resolution in the usbtv struct, but the video plane buffer isn't adjusted, so it overflows.
[hverkuil: call vb2_is_busy instead of vb2_is_streaming]
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Analysis
by VulDB Data Team • 02/09/2026
The vulnerability CVE-2025-39714 represents a critical memory management flaw within the Linux kernel's USB TV streaming subsystem, specifically affecting the usbtv driver component. This issue manifests when concurrent processes attempt to modify video streaming parameters during active media transmission, creating a race condition that leads to kernel crashes and system instability. The flaw occurs within the media framework where the kernel fails to properly synchronize buffer allocation updates with active streaming operations, demonstrating a fundamental weakness in resource management protocols that govern multimedia device operations.
The technical root cause stems from improper locking mechanisms during video standard transitions within the USB TV streaming driver. When a streaming application like ffplay operates continuously while another utility such as qv4l2 attempts to switch the TV standard from NTSC to PAL, the kernel's memory management system encounters a critical inconsistency. The transition from NTSC to PAL inherently requires increased resolution parameters within the usbtv structure, yet the associated video plane buffers remain unadjusted to accommodate the expanded memory requirements. This discrepancy results in attempts to write data to memory regions that have not been properly mapped or allocated, leading to immediate kernel panics and system termination.
The operational impact of this vulnerability extends beyond simple system crashes to encompass potential data corruption and service disruption in multimedia applications. Attackers could exploit this weakness to cause denial of service conditions in systems relying on USB TV receivers, particularly affecting media servers, digital video recording systems, and embedded multimedia platforms. The vulnerability specifically targets the vb2 (video buffer 2) subsystem integration where the kernel incorrectly uses vb2_is_streaming instead of the more appropriate vb2_is_busy function, creating a scenario where buffer states are not properly validated before memory operations occur. This misconfiguration allows for simultaneous access to memory regions that should remain locked during active streaming operations, violating fundamental principles of concurrent system design.
Security implications of this vulnerability align with CWE-362, which addresses race conditions in concurrent execution environments, and relate to ATT&CK technique T1499.004 for network denial of service. The flaw demonstrates inadequate input validation and resource management within kernel space operations, particularly in multimedia device drivers where timing-sensitive buffer operations must maintain strict synchronization protocols. Organizations deploying Linux-based multimedia systems should consider immediate mitigation strategies including kernel version updates, process isolation for streaming operations, and implementation of proper locking mechanisms to prevent concurrent buffer modification during active media transmission. The vulnerability underscores the critical importance of proper resource management in kernel-level drivers and highlights the necessity of comprehensive testing for concurrent access scenarios in multimedia subsystems.