CVE-2026-99196 in Linux
Summary
by MITRE • 10/28/2026
In the Linux kernel, the following vulnerability has been resolved:
net: au1000: move setting of netops to fix crash
au1000_probe() calls au1000_mii_probe(), which connects the PHY, before dev->netdev_ops is assigned. phy_attach_direct() -> phy_link_topo_add_phy() reads dev->netdev_ops through netdev_need_ops_lock() since the commit in question, so probing crashes with a NULL pointer dereference when CONFIG_NET_SHAPER is enabled.
Assign netdev_ops before the PHY attach, as was done for emac in commit 7c9f391ec89c ("net: emac: move setting of netops to fix crash").
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Analysis
by VulDB Data Team • 10/28/2026
The vulnerability identified within the Linux kernel involves a critical NULL pointer dereference located in the au1000 network driver. This issue arises from an incorrect initialization sequence during the device probing phase, specifically when the CONFIG_NET_SHAPER configuration option is enabled. The root cause lies in the order of operations performed by the au1000_probe function relative to the assignment of the netdev_ops structure. In this flawed implementation, the driver attempts to connect the PHY via au1000_mii_probe before dev->netdev_ops has been assigned a valid value. This sequencing error creates a window where internal kernel networking subsystems expect certain operations structures to be present but find them uninitialized or null.
The technical flaw is triggered by the phy_attach_direct function, which subsequently calls phy_link_topo_add_phy. Within this call chain, the netdev_need_ops_lock function attempts to access dev->netdev_ops to determine locking requirements for network device operations. Because the pointer has not yet been initialized at this stage of execution, the kernel encounters a NULL reference. This results in an immediate crash or panic during system boot when the driver is loaded, effectively rendering the associated hardware non-functional and potentially causing broader system instability depending on how the kernel handles such exceptions.
From a classification perspective, this vulnerability aligns with CWE-476, which denotes a NULL Pointer Dereference. The error occurs because the software fails to check for null pointers before using them in operations that require valid memory references. In terms of attack vectors and behavioral mapping under the MITRE ATT&CK framework, while this is primarily an unintentional stability issue rather than a malicious exploit vector, it represents a failure in proper resource initialization logic. Such errors can sometimes be leveraged by attackers to cause denial-of-service conditions if they can trigger specific driver loading sequences or kernel module initializations that expose these race-like timing issues during system startup.
The operational impact of this vulnerability is significant for systems relying on the au1000 Ethernet controller, particularly those compiled with network shaper support enabled. The immediate consequence is a kernel panic upon booting if the hardware is detected and the driver attempts to initialize. This prevents the network interface from coming online, disrupting connectivity for any services dependent on that specific network adapter. For embedded systems or industrial control environments where au1000 chips are commonly used, this can lead to complete system unavailability until a patch is applied or the configuration option is disabled.
The resolution involves reordering the initialization steps within the au1000_probe function. By assigning dev->netdev_ops before calling au1000_mii_probe and subsequently phy_attach_direct, the kernel ensures that any subsequent calls to netdev_need_ops_lock will find a valid pointer structure in memory. This fix mirrors similar corrections applied to other drivers such as emac, ensuring consistency across the network subsystem's initialization patterns. Administrators should apply this patch or update their kernels to versions where this ordering correction is included. Additionally, verifying that CONFIG_NET_SHAPER settings are compatible with updated driver code can prevent recurrence of related issues in future kernel builds.