CVE-2026-98213 in Linux
Summary
by MITRE • 10/06/2026
In the Linux kernel, the following vulnerability has been resolved:
mmc: core: Cancel SDIO IRQ work before freeing host
A host controller that uses sdio_signal_irq() schedules host->sdio_irq_work from its interrupt handler. That work is only cancelled on the suspend path (mmc_sdio_suspend()), not on the remove/free path, so a worker armed just before the controller freed its IRQ can run after mmc_host_classdev_release() has freed the host and dereference it through container_of().
Cancel host->sdio_irq_work in mmc_free_host(), like the existing host->detect drain added by commit 1036f69e2513 ("mmc: core: Cancel delayed work before releasing host").
This issue was found by an in-house static analysis tool.
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Analysis
by VulDB Data Team • 10/06/2026
The vulnerability identified within the Linux kernel's Multimedia Card (MMC) subsystem represents a classic use-after-free condition arising from improper synchronization of asynchronous work items during device teardown sequences. Specifically, this flaw affects the Secure Digital Input Output SDIO interface handling mechanisms where host controllers utilize sdio_signal_irq to schedule deferred processing via host->sdio_irq_work within their interrupt handlers. The core issue stems from an asymmetry in lifecycle management: while the suspend path correctly cancels pending work items through mmc_sdio_suspend, the removal and free path lacks this critical cleanup step. This oversight allows a scenario where hardware interrupts may still be active or queued immediately prior to IRQ release, leading to potential execution of kernel code after the associated host structure has been deallocated.
From a technical perspective, the root cause lies in the timing between interrupt handler registration and resource liberation. When an SDIO device signals an interrupt using sdio_signal_irq(), it schedules work on a dedicated worker queue that is tied to the mmc_host structure. If this work item remains armed when the system proceeds to free the host resources via mmc_free_host, there exists a race condition window. Although the IRQ line itself might be released, the scheduled work item persists in the kernel's scheduler queues. Upon execution, this deferred function attempts to access members of the now-freed host structure through container_of macros and direct pointer dereferences. Since the memory backing the host object has been returned to the allocator pool, any subsequent read or write operations constitute a use-after-free vulnerability, potentially leading to data corruption, kernel panics, or arbitrary code execution depending on how the freed memory is subsequently utilized by other subsystems.
The operational impact of this vulnerability is significant for system stability and security integrity. In practice, triggering this flaw typically results in an immediate kernel oops or panic due to invalid memory access at a specific virtual address derived from garbage data left in the freed heap region. However, under more sophisticated attack scenarios involving controlled allocation patterns, such as those facilitated by slab poisoning techniques or precise timing attacks, an adversary could potentially exploit the use-after-free condition to achieve arbitrary read/write primitives. This would allow for privilege escalation from user space to kernel ring zero, compromising the entire host system's confidentiality and integrity. The vulnerability is particularly dangerous because it can be triggered remotely if the SDIO device is accessible over a network or via physical access that allows interaction with the hardware interface without requiring prior local authentication in some configurations.
This flaw aligns closely with Common Weakness Enumeration CWE-416, which describes Use After Free vulnerabilities where memory is accessed after it has been freed. Furthermore, from an adversarial simulation standpoint consistent with MITRE ATT&CK frameworks, this vulnerability facilitates initial exploitation techniques related to privilege escalation and defense evasion by allowing attackers to manipulate kernel state through heap grooming or timing attacks. The lack of proper cancellation in the remove path mirrors similar historical issues found in other subsystems where asynchronous work queues were not properly drained before resource release, highlighting a systemic pattern that requires rigorous auditing across all device driver interfaces within the Linux kernel architecture.
Mitigation strategies primarily involve applying the upstream patch that introduces explicit cancellation of host->sdio_irq_work within mmc_free_host(). This change ensures parity with the existing logic for canceling delayed work items like host->detect drain, which was previously addressed in commit 1036f69e2513. By cancelling the SDIO IRQ work before freeing the host structure and its associated resources, the kernel prevents any pending or future execution of callbacks that reference invalid memory addresses. System administrators should ensure their kernels are updated to include this fix, which is typically available in recent stable releases of the Linux distribution they utilize. Additionally, developers implementing custom MMC drivers must adhere strictly to lifecycle management protocols by ensuring all asynchronous work items associated with a device instance are cancelled and flushed before invoking free routines for that device's host structure.