CVE-2026-97513 in Linux
Summary
by MITRE • 09/24/2026
In the Linux kernel, the following vulnerability has been resolved:
media: chips-media: wave5: Release m2m_ctx after Instance Removed from List
Possible use after free if IRQ thread manages to obtain spinlock between m2m_ctx release and wave5_release function removing stream instance from list of active instances. The IRQ thread looks for the m2m_ctx which is freed so null pointer dereference occurs.
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Analysis
by VulDB Data Team • 09/24/2026
The vulnerability identified in the Linux kernel media subsystem, specifically within the chips-media: wave5 driver, represents a critical race condition that leads to a use-after-free scenario and subsequent null pointer dereference. This flaw arises from an improper synchronization mechanism during the lifecycle management of memory-to-memory context structures. The core issue lies in the sequence of operations performed when releasing resources associated with a video stream instance. Specifically, there is a window where the m2m_ctx structure is released or freed before it is safely removed from the global list of active instances managed by the driver. This temporal gap creates an opportunity for concurrent execution paths to access memory that has already been deallocated, violating fundamental principles of kernel memory safety and concurrency control.
The technical mechanism behind this vulnerability involves a race between the main release function and the interrupt request thread handler. When the wave5_release function is invoked to tear down a stream instance, it must ensure that no other threads are currently accessing or referencing the associated context data structures. However, in the flawed implementation, the m2m_ctx structure may be freed while still being referenced by an active IRQ thread. If the interrupt thread manages to acquire the relevant spinlock during this narrow interval between the release of the context and its removal from the instance list, it will attempt to dereference a pointer that no longer points to valid memory. This results in a null pointer dereference or access to freed memory, which typically causes an immediate kernel panic or system crash due to the protection mechanisms enforced by modern operating systems against such illegal memory accesses.
From an operational impact perspective, this vulnerability allows for local denial of service attacks. An attacker with sufficient privileges to trigger the media stream release process can exploit this race condition to destabilize the entire Linux kernel environment. The resulting null pointer dereference leads to a system crash, rendering the device unusable until it is rebooted. This is particularly concerning in embedded systems or servers where continuous uptime is critical and where multiple users might be interacting with video processing hardware concurrently. The lack of proper synchronization means that under high load conditions, where interrupt handling frequency increases, the probability of hitting this race window significantly rises, making the vulnerability practically exploitable rather than merely theoretical.
To mitigate this risk, developers must enforce strict ordering in resource deallocation sequences within the driver code. The primary fix involves ensuring that the stream instance is removed from the list of active instances before any associated context structures are freed or released. This guarantees that no concurrent thread can locate and attempt to access a dangling pointer through the global registry of active streams. Additionally, implementing robust locking strategies that cover both the removal operation and the subsequent memory release ensures atomicity in these critical sections. It is also advisable to add explicit checks within the interrupt handler to verify the validity of pointers before dereferencing them, although relying solely on defensive programming without fixing the root cause synchronization issue is not a complete solution.
This vulnerability aligns with CWE-416, which describes Use After Free errors, where program execution continues after memory has been freed, leading to undefined behavior and potential security breaches. Furthermore, it relates to CWE-362, Concurrent Execution using Shared Resource with Improper Synchronization, as the root cause is a failure to properly synchronize access to shared data structures between different execution contexts such as process context and interrupt context. In terms of adversary tactics, this flaw could be leveraged in ATT&CK technique T1499, Endpoint Denial of Service, where an attacker aims to disrupt availability by causing system crashes through resource exhaustion or race conditions rather than exploiting code execution vulnerabilities for privilege escalation. Addressing these synchronization issues is essential for maintaining the integrity and reliability of media processing subsystems within the Linux kernel ecosystem.