CVE-2026-23253: 
Linux Kernel vulnerability analysis and mitigation

CVE-2026-23253 is a Linux kernel vulnerability in the DVB (Digital Video Broadcasting) subsystem, specifically in the dvb_dvr_open() function of the media: dvb-core driver. The flaw involves incorrect reinitialization of the DVR ringbuffer's waitqueue on device reopen, which can lead to kernel memory corruption and denial of service. It was disclosed on March 18, 2026, and affects Linux kernel versions from 2.6.17 through multiple stable branches up to 6.19. It carries a CVSS v3.1 base score of 7.8 (High) (Red Hat Advisory, Red Hat Bugzilla).

The root cause is improper reinitialization of a shared kernel data structure (CWE-665: Improper Initialization). When dvb_dvr_open() is called for a new reader, it invokes dvb_ringbuffer_init(), which in turn calls init_waitqueue_head() — resetting the shared waitqueue dmxdev->dvr_buffer.queue to an empty state. This orphans any existing waitqueue entries from io_uring poll or epoll operations, leaving them with stale prev/next pointers while the list head is reset to {self, self}. The fix replaces the dvb_ringbuffer_init() call with direct assignment of data/size fields and a call to dvb_ringbuffer_reset(), which correctly resets read/write positions without disturbing the waitqueue or spinlock that were already initialized in dvb_dmxdev_init() (Red Hat Bugzilla, Kernel Patch).

A local user with permissions to access the DVR device node can trigger kernel memory corruption by opening the device multiple times while io_uring poll or epoll operations are pending. This results in use-after-free-like conditions due to stale waitqueue pointers, potentially causing system crashes, kernel panics, or hangs — a denial of service impact. Confidentiality and integrity impacts are also rated High in the CVSS score, suggesting the memory corruption could theoretically be leveraged for privilege escalation, though the primary documented impact is availability (Red Hat Advisory, Red Hat Bugzilla).

Apply the latest kernel security updates for the affected stable branches. Fixed versions include: 5.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.77, 6.18.17, and 6.19.7 (Red Hat Advisory). Upstream patches are available in the kernel stable tree (Kernel Patch). As a temporary workaround where upgrading is not immediately possible, restrict access to DVR device nodes (e.g., /dev/dvb/) to trusted users only via filesystem permissions or udev rules. Distribution-specific updates have been issued by Debian (DSA-6238-1, DSA-6243-1, DLA-4561-1), SUSE (SUSE-SU-2026:2217-1, SUSE-SU-2026:2238-1), and Microsoft Azure Linux (SUSE Advisory, Debian Advisory).