CVE-2026-89998 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
dm: fix race when loading and unloading a table
If the userspace calls two concurrent table load ioctls and one of them succeeds and the other fails, there is a race condition because dm_setup_md_queue walks &md->table_devices without any lock. If the walk races with dm_table_destroy -> free_devices -> dm_put_table_device, there is access to invalid memory.
Fix this race by extending the lock over the list walk.
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Analysis
by VulDB Data Team • 09/17/2026
The Linux kernel device mapper subsystem contains a critical concurrency flaw related to the management of table devices during load and unload operations. This vulnerability arises from an insufficient locking mechanism when accessing shared data structures, specifically within the dm_setup_md_queue function which iterates over the md->table_devices list without holding any synchronization locks. In high-concurrency scenarios where userspace applications issue multiple ioctl calls simultaneously for loading device mapper tables, this lack of protection creates a window for race conditions that can compromise system stability and security.
The core technical flaw involves an asynchronous access to memory structures that are subject to concurrent modification or destruction. When one table load operation succeeds while another fails, the kernel may attempt to walk the list of table devices without proper serialization. If this iteration occurs concurrently with a dm_table_destroy call which triggers free_devices and subsequently dm_put_table_device, the system risks accessing invalid or freed memory addresses. This scenario represents a classic use-after-free condition where pointers are dereferenced after the underlying objects have been deallocated by another thread of execution.
From an industry standards perspective, this vulnerability aligns with CWE-362, which describes concurrent access to shared resources without proper synchronization leading to race conditions. Furthermore, it relates closely to CWE-416, use-after-free errors, as the primary consequence is accessing memory that has already been released back to the system allocator. In terms of attack vectors and tactics, this flaw can be leveraged in contexts where local privilege escalation or denial of service are targeted, mapping towards ATT&CK techniques involving exploitation of race conditions for resource manipulation or stability disruption within kernel space.
The operational impact of this vulnerability is significant as it allows a local attacker to trigger undefined behavior by crafting specific sequences of ioctl calls that exploit the timing window between table loading and unloading processes. Successful exploitation could lead to kernel panics, resulting in a denial of service against the host system. In more severe cases, depending on memory layout and heap state at the time of access, it might enable arbitrary code execution with kernel privileges, thereby compromising the integrity and confidentiality of all data managed by that machine.
To mitigate this risk, the vulnerability has been addressed by extending the lock scope to encompass the entire list walk operation within dm_setup_md_queue. This ensures mutual exclusion during critical sections where table devices are accessed or modified. System administrators should apply kernel updates provided by their distribution vendors as soon as they become available. Additionally, implementing strict access controls on device mapper interfaces and monitoring for unusual patterns of concurrent ioctl calls can help reduce the attack surface until patches are fully deployed across all affected systems.