CVE-2026-98494 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
net: atl1: fix soft lockup on out-of-range cmb_tpd_next_to_clean read
Same issue as atl1c (see the first commit in this series, "net: atl1c: fix soft lockup on out-of-range tpd_cons read"): the hardware can report an out-of-range cmb_tpd_next_to_clean (seen as 0xffff) while the PCIe link/MAC is resetting. An out-of-range value can never be reached and the loop below would spin forever. Treat it as "nothing new to clean" instead.
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Analysis
by VulDB Data Team • 10/18/2026
The vulnerability identified in the Linux kernel network driver for Atheros AR813x/AR8152 Ethernet controllers, specifically within the atl1 module, represents a critical stability issue rooted in improper handling of hardware state during link resets. The core technical flaw lies in how the driver processes the cmb_tpd_next_to_clean register value when reading from the Transmit Descriptor Ring. Under normal operational conditions, this pointer indicates the next descriptor to be cleaned after transmission completion. However, during periods where the PCIe link or Media Access Control layer is undergoing a reset sequence, the hardware may report an anomalous out-of-range value for this field, specifically manifesting as 0xffff. This specific hexadecimal value signifies that no valid descriptors are available for processing at that moment due to the transitional state of the hardware interface.
The operational impact of this flaw is severe and directly affects system availability through a soft lockup condition. The driver's cleanup loop relies on comparing current descriptor pointers against previous ones to determine if new work needs to be processed. When the out-of-range value 0xffff is encountered, it does not align with any valid memory address or expected state within the descriptor ring logic. Consequently, the conditional checks designed to break the loop fail because the invalid pointer cannot be logically reconciled as a reachable position in the sequence. This causes the execution thread to enter an infinite spin loop, consuming CPU cycles indefinitely and preventing other kernel tasks from executing on that processor core. Such behavior effectively freezes the network subsystem and can lead to broader system instability or unresponsiveness depending on which process holds the lock during this event.
This issue mirrors a previously resolved vulnerability in the atl1c driver variant, highlighting a common pattern of race conditions between hardware state transitions and software polling mechanisms in legacy Atheros Ethernet drivers. The root cause is fundamentally a lack of boundary validation for values returned by hardware registers that are subject to change during asynchronous events like link resets. By failing to detect this specific sentinel value indicative of an invalid or reset state, the driver assumes there is pending work when none exists, leading directly to the denial-of-service scenario characterized by CPU saturation and process hang.
To mitigate this vulnerability, the implemented fix introduces explicit validation logic that treats the out-of-range 0xffff value as a signal indicating no new descriptors require cleaning. This approach aligns with defensive programming practices recommended in industry standards such as CWE-835 regarding loop-invariant conditions or infinite loops caused by improper state management. By correctly interpreting this hardware artifact, the driver avoids entering the problematic spin loop and maintains system stability even during transient link reset events. System administrators should ensure that kernel updates incorporating this patch are applied to affected systems running older Atheros-based network interfaces to prevent potential service disruptions arising from these specific hardware-software interaction edge cases.