CVE-2026-98429 in Linux
Summary
by MITRE • 10/14/2026
In the Linux kernel, the following vulnerability has been resolved:
RDMA/efa: Keep EQ resources alive while IRQ is registered
The completion IRQ handler accesses the EQ state and DMA buffer. Its IRQ was registered before that state was initialized, while teardown released the buffer before free_irq() synchronized the handler.
Initialize the EQ without arming it, register the IRQ, and then arm it. Reverse the resource order during teardown by freeing the IRQ before destroying the EQ.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 10/14/2026
The Linux kernel vulnerability identified in the RDMA EFA driver involves a critical race condition related to the initialization and teardown of Event Queue resources and their associated Interrupt Request handlers. This flaw stems from an incorrect ordering of operations when setting up or tearing down hardware interrupt handling mechanisms, leading to potential access of uninitialized memory structures or freed buffers during active processing. The specific component affected is the Elastic Fabric Adapter driver within the RDMA subsystem, which manages communication between instances in AWS environments and requires precise synchronization for reliable operation under high load conditions.
During the initialization phase, the completion IRQ handler was registered before the Event Queue state and its associated DMA buffer were fully initialized. This sequence creates a window of vulnerability where an interrupt could be triggered immediately upon registration but before the necessary data structures are ready to handle it safely. If such an event occurs during this brief interval, the kernel may attempt to access memory regions that have not been properly allocated or configured by the driver. This can result in undefined behavior, including potential system crashes, data corruption, or security breaches if malicious actors exploit this state to execute arbitrary code through crafted interrupt signals or buffer overflows resulting from accessing uninitialized pointers.
The teardown process exhibits a complementary flaw where resources are released in an incorrect order relative to their usage by the kernel's interrupt subsystem. Specifically, the DMA buffer associated with the Event Queue was freed before calling free_irq(), which is responsible for synchronizing and disabling the IRQ handler. Since the IRQ handler retains references to these buffers during its execution window, freeing them prematurely leaves dangling pointers within active or pending interrupt contexts. When the system attempts to process completions via this handler after the buffer has been deallocated but before the IRQ line is fully disconnected, it accesses invalid memory addresses. This scenario mirrors classic use-after-free vulnerabilities where previously allocated and subsequently freed memory is accessed by running processes or kernel threads without proper synchronization barriers ensuring exclusive access.
From a technical perspective, this issue aligns with CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization, as the race condition arises from improper ordering of resource allocation versus handler registration. It also relates to CWE-416: Use After Free, given that the teardown sequence allows access to freed DMA buffers through lingering IRQ handlers. In terms of MITRE ATT&CK mapping, this vulnerability could potentially be leveraged for privilege escalation or denial-of-service attacks by triggering kernel panics or exploiting memory corruption states if an attacker can influence interrupt timing or trigger specific RDMA operations under constrained resource conditions. The lack of atomicity in these setup and teardown sequences represents a fundamental design flaw in the driver's lifecycle management logic rather than a simple coding error, requiring structural changes to ensure safe state transitions.
The operational impact of this vulnerability includes potential system instability, data integrity issues, and security risks depending on how an attacker might exploit the race condition or use-after-free scenario. In production environments running RDMA workloads, particularly those involving large-scale distributed computing frameworks like Apache Spark or Hadoop over InfiniBand-like fabrics, such instabilities could lead to service disruptions affecting multiple tenants sharing physical infrastructure. Furthermore, because DMA buffers are involved, there is a risk of cross-tenant data leakage if memory isolation boundaries are breached due to improper handling of shared resources during interrupt processing windows.
To mitigate this vulnerability, the Linux kernel community has implemented a fix that reorders the initialization and teardown sequences strictly according to safety requirements. During initialization, the Event Queue state must be established without arming it immediately; instead, the IRQ handler should be registered first while in a dormant state, followed by explicitly arming the EQ only after all prerequisites are confirmed ready. This ensures no interrupts can fire until the system is fully prepared to handle them safely. Conversely, during teardown, the order of operations must be reversed: the IRQ handler must be freed and synchronized using free_irq() before destroying the Event Queue resources. This guarantees that any pending or in-flight interrupt handlers complete their execution against valid memory structures before those structures are deallocated, eliminating both the race condition window and the use-after-free possibility.
Administrators managing systems with affected kernel versions should apply the latest available patches to ensure these synchronization issues are resolved. For organizations unable to patch immediately due to compatibility constraints, monitoring RDMA subsystem logs for unexpected errors or crashes may provide early warning signs of exploitation attempts. Additionally, enforcing strict resource management policies and avoiding manual manipulation of low-level driver states can reduce exposure risks until formal updates are deployed across the infrastructure landscape.