CVE-2026-64587 in Linux
Summary
by MITRE • 08/06/2026
In the Linux kernel, the following vulnerability has been resolved:
net: ethernet: arc: emac: quiesce interrupts before requesting IRQ
Normal RX/TX interrupts are enabled later, in arc_emac_open(), so probe should not see interrupt delivery in the usual case. However, hardware may still present stale or latched interrupt status left by firmware or the bootloader.
If probe later unwinds after devm_request_irq() has installed the handler, such a stale interrupt can still reach arc_emac_intr() during teardown and race with release of the associated net_device.
Avoid that window by putting the device into a known quiescent state before requesting the IRQ: disable all EMAC interrupt sources and clear any pending EMAC interrupt status bits. This keeps the change hardware-focused and minimal, while preventing spurious IRQ delivery from leftover state.
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Analysis
by VulDB Data Team • 08/06/2026
This vulnerability exists in the Linux kernel's ARC EMAC network driver where improper interrupt handling during device probe can lead to race conditions and potential system instability. The issue stems from the sequence of operations during driver initialization where interrupt sources are not properly managed before requesting IRQ handlers, creating a window where stale interrupt status from previous firmware or bootloader execution can cause unexpected behavior.
The technical flaw manifests when the arc_emac_probe function calls devm_request_irq() to install the interrupt handler, but fails to quiesce the interrupt state beforehand. While normal RX/TX interrupts are typically enabled later in the arc_emac_open() function, hardware may retain stale or latched interrupt status bits that were left behind by firmware or bootloader components. This creates a dangerous scenario where an interrupt can be delivered to arc_emac_intr() during driver teardown operations, causing a race condition between the interrupt handler and net_device resource cleanup.
The operational impact of this vulnerability extends beyond simple interrupt handling issues to potentially compromise system stability and security. When stale interrupts trigger during device removal or driver unloading, they can cause memory corruption, null pointer dereferences, or other undefined behaviors that may lead to system crashes or privilege escalation opportunities. The race condition between interrupt delivery and resource release creates an attack surface where malicious actors could potentially exploit this timing window to manipulate kernel data structures or execute arbitrary code.
The proposed mitigation strategy focuses on maintaining a hardware-focused approach by disabling all EMAC interrupt sources and clearing pending interrupt status bits before requesting the IRQ handler. This minimal change ensures that the device enters a known quiescent state, preventing spurious interrupt delivery from leftover firmware or bootloader state. The solution directly addresses the root cause identified in CWE-691, which deals with insufficient control flow management in interrupt handling, and aligns with ATT&CK technique T1068 by preventing privilege escalation through improper resource management. By implementing this quiescing mechanism before IRQ request operations, the driver eliminates the window where stale interrupts could interfere with normal device operation or cleanup procedures.
This fix demonstrates proper defensive programming practices in kernel development where hardware state management is critical for maintaining system integrity during driver initialization and teardown phases. The approach ensures that interrupt handling operates predictably regardless of previous firmware or bootloader execution states, reducing the attack surface and improving overall system reliability. The minimal nature of this change reduces risk of introducing new issues while effectively addressing the specific race condition vulnerability present in the ARC EMAC driver implementation.