CVE-2026-98973 in Linux
Summary
by MITRE • 10/23/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/bridge: Fix unlocked list_del in drm_bridge_add()
When re-adding a bridge that was previously removed, drm_bridge_add() drops it from bridge_lingering_list without holding bridge_lock.
Both bridge_list and bridge_lingering_list are protected by bridge_lock, as they are concurrently modified by drm_bridge_remove() and __drm_bridge_free(), and walked by the debugfs 'bridges' file. Running the list_empty() test and the list_del_init() outside of the lock may therefore corrupt either list.
Perform both under bridge_lock.
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Analysis
by VulDB Data Team • 10/23/2026
The Linux kernel's Direct Rendering Manager subsystem contains a critical concurrency vulnerability within the drm_bridge_add function, specifically involving improper synchronization when managing bridge device lists. This flaw arises during the process of re-adding a display bridge that was previously removed from the system. In this specific operational scenario, the code attempts to remove the bridge entry from the bridge_lingering_list without acquiring the necessary bridge_lock mutex. The underlying technical architecture relies on bridge_lock as the primary synchronization primitive for both the main bridge_list and the auxiliary bridge_lingering_list. These data structures are subject to concurrent modifications by functions such as drm_bridge_remove and __drm_bridge_free, while simultaneously being read during debugfs operations via the bridges file interface. By executing list_empty checks and subsequent list_del_init calls outside the protection of this lock, the kernel exposes itself to race conditions that can lead to memory corruption or undefined behavior within the linked lists managing display hardware state.
The operational impact of this vulnerability is significant for system stability and security integrity. The lack of proper locking means that concurrent access from different execution contexts can corrupt the internal pointers of the doubly-linked lists, potentially leading to kernel panics, data leaks through corrupted memory structures, or denial of service conditions where the display subsystem becomes unresponsive. This type of flaw aligns with CWE-362, which describes Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). The vulnerability allows an attacker who can trigger the removal and subsequent re-addition of a bridge device to exploit this race window, potentially destabilizing the kernel or gaining unauthorized access to sensitive memory regions associated with display driver state.
From a threat modeling perspective, this issue relates to ATT&CK techniques involving resource manipulation and potential privilege escalation if the corrupted data structures are leveraged for further exploitation. The fix implemented in the patch resolves this by ensuring that both the list_empty test and the list_del_init operation are performed while holding the bridge_lock mutex. This guarantees mutual exclusion during critical sections where shared resources are modified, thereby preventing race conditions and maintaining the integrity of the kernel's internal data structures. System administrators should ensure their kernels are updated to include this patch to mitigate risks associated with concurrent display driver operations.