CVE-2026-23253 in Linux
Summary
by MITRE • 03/18/2026
In the Linux kernel, the following vulnerability has been resolved:
media: dvb-core: fix wrong reinitialization of ringbuffer on reopen
dvb_dvr_open() calls dvb_ringbuffer_init() when a new reader opens the DVR device. dvb_ringbuffer_init() calls init_waitqueue_head(), which reinitializes the waitqueue list head to empty.
Since dmxdev->dvr_buffer.queue is a shared waitqueue (all opens of the same DVR device share it), this orphans any existing waitqueue entries from io_uring poll or epoll, leaving them with stale prev/next pointers while the list head is reset to {self, self}.
The waitqueue and spinlock in dvr_buffer are already properly initialized once in dvb_dmxdev_init(). The open path only needs to reset the buffer data pointer, size, and read/write positions.
Replace the dvb_ringbuffer_init() call in dvb_dvr_open() with direct assignment of data/size and a call to dvb_ringbuffer_reset(), which properly resets pread, pwrite, and error with correct memory ordering without touching the waitqueue or spinlock.
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Analysis
by VulDB Data Team • 06/02/2026
The vulnerability identified as CVE-2026-23253 resides within the Linux kernel's digital video broadcast subsystem, specifically in the dvb-core module that manages DVB device operations. This issue affects the DVB Digital Video Recorder (DVR) device handling mechanism where improper reinitialization occurs during device reopen operations. The flaw manifests when multiple processes attempt to access the same DVR device through different file descriptors, creating a scenario where shared resources become corrupted due to incorrect state management. The vulnerability represents a classic case of improper resource handling that can lead to system instability and potential security implications within embedded systems that rely on Linux kernel media subsystems.
The technical root cause stems from the dvb_dvr_open() function which incorrectly invokes dvb_ringbuffer_init() during device reopening operations. This function call performs more than just buffer initialization - it includes a call to init_waitqueue_head() that resets the waitqueue list head to an empty state. When multiple readers open the same DVR device, they share the same dvr_buffer.queue waitqueue structure, making this reinitialization operation particularly dangerous. The shared waitqueue nature means that existing waitqueue entries from io_uring poll or epoll operations become orphaned, leaving behind stale prev/next pointers while the list head is reset to its initial {self, self} state. This creates a memory corruption scenario that can lead to system crashes or unpredictable behavior when the corrupted waitqueue entries are subsequently accessed.
The operational impact of this vulnerability extends beyond simple system instability to potentially enable privilege escalation or denial of service conditions within systems that utilize DVB devices. The improper handling of shared waitqueue structures can cause kernel memory corruption that may be exploitable by malicious actors who can trigger the vulnerable code path through multiple concurrent DVR device access attempts. Systems using Linux-based set-top boxes, digital television receivers, or embedded media processing equipment are particularly at risk since these platforms often maintain long-running processes that access DVB devices multiple times. The vulnerability affects the fundamental reliability of media subsystem operations and can compromise the integrity of real-time data processing pipelines that depend on consistent DVR device behavior.
The fix implemented addresses the core issue by replacing the problematic dvb_ringbuffer_init() call with a more targeted approach that preserves existing waitqueue and spinlock initialization while properly resetting only the buffer data pointer, size, and read/write positions. The solution introduces direct assignment of data and size parameters followed by a call to dvb_ringbuffer_reset() which properly handles the reset of pread, pwrite, and error values with correct memory ordering. This approach ensures that the shared waitqueue and spinlock structures remain intact while only the necessary buffer state information is reset, preventing the corruption of existing waitqueue entries. The mitigation aligns with security best practices for kernel development and follows established patterns for resource management in concurrent systems. This fix resolves the immediate vulnerability while maintaining backward compatibility and system stability, addressing the underlying CWE-362 concurrency issue that makes this vulnerability exploitable in real-world scenarios.