CVE-2026-74741 in Linux
Summary
by MITRE • 08/26/2026
In the Linux kernel, the following vulnerability has been resolved:
net: ngbe: fix NULL pointer dereference in non-MSI-X interrupt enabling
In non-MSI-X mode (such as legacy INTx or single MSI), wx->msix_entry is not allocated or initialized. Calling NGBE_INTR_MISC(wx) dereferences wx->msix_entry->entry, leading to a NULL pointer dereference crash.
This issue was introduced by fixing the IRQ vector when the number of VFs is 7. Fix the issue by explicitly checking `pdev->msix_enabled` to determine the correct vector index.
Additionally, as a side fix, set the interrupt mask to BIT(0) for the non-MSI-X fallback. In MSI/INTx mode, the MISC and queue interrupts share vector 0, and the WX_PX_MISC_IVAR register is only valid in the MSI-X case. Thus, BIT(0) is the correct mask for the miscellaneous cause when MSI-X is disabled.
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Analysis
by VulDB Data Team • 08/26/2026
The Linux kernel driver for the NGBE network interface contains a critical memory safety flaw that manifests as a NULL pointer dereference during interrupt initialization under specific hardware configuration scenarios. This vulnerability arises from an incorrect assumption regarding the allocation and availability of MSIX entry structures within the device context structure. Specifically, when the system operates in non-MSI-X modes, such as legacy INTx or single MSI interrupts, the driver fails to allocate or initialize the msix_entry field because these interrupt mechanisms do not utilize the multi-vector table associated with Message Signaled Interrupts Extension. Consequently, any subsequent attempt to access this uninitialized pointer results in a kernel panic due to dereferencing a NULL address, effectively causing a denial of service by crashing the host system during network interface initialization or reset operations.
The root cause of this defect is traced back to a previous patch intended to correct IRQ vector allocation when seven Virtual Functions are present on the device. That fix inadvertently introduced logic that blindly accessed the msix_entry structure without verifying whether MSIX was actually enabled for the PCI function. The technical flaw lies in the use of the NGBE_INTR_MISC macro, which internally dereferences wx->msix_entry to retrieve the entry index. In environments where MSI-X is disabled, this pointer remains NULL because the driver correctly skips the allocation step for non-MSI-X configurations. This oversight highlights a common pattern in kernel development where assumptions about hardware capabilities or configuration states are not sufficiently validated before memory access occurs, leading to stability issues across various deployment scenarios that do not support advanced interrupt routing features.
From an operational perspective, this vulnerability allows any local user with the ability to trigger network interface resets or probe operations for devices using the NGBE driver to cause a system crash. Since the flaw is triggered during the setup of interrupt handling mechanisms, it can be exploited by unprivileged users who have access to device nodes or can influence driver loading sequences through standard administrative tools that do not require root privileges if they are part of automated provisioning scripts or containerized workloads with specific network namespace configurations. The impact extends beyond simple availability loss; a kernel panic results in the immediate termination of all processes on the affected system, leading to significant downtime and potential data corruption for running services depending on the stability of that host node.
To mitigate this vulnerability, it is essential to apply the upstream Linux kernel patch that explicitly checks the pdev->msix_enabled flag before attempting to access MSIX-specific structures. This validation ensures that the driver only dereferences msix_entry when the hardware and operating system have successfully negotiated MSI-X support. Additionally, for non-MSI-X fallback modes such as legacy INTx or single MSI, the interrupt mask must be correctly set to BIT(0). This adjustment is necessary because in these modes, miscellaneous interrupts and queue interrupts share vector 0, and the WX_PX_MISC_IVAR register used for individual vector assignment is only valid when MSIX is active. By aligning the interrupt masking logic with the actual hardware behavior of non-MSI-X configurations, the driver avoids undefined behavior and ensures stable operation across all supported interrupt types.
This vulnerability maps to CWE-476, which describes a NULL pointer dereference error where software incorrectly assumes that a pointer will never be null before using it. In terms of attack vectors, this aligns with ATT&CK technique T1053, specifically the Scheduled Task/Job or Service execution aspects if an attacker can manipulate system initialization sequences to trigger the vulnerable code path during boot or service restart. Furthermore, it relates to CWE-20 regarding improper input validation, as the driver fails to validate the state of PCI capabilities before proceeding with hardware-specific configuration steps. Remediation requires updating the kernel package on affected systems and ensuring that all network interface drivers are compiled against a patched source tree that includes these safety checks for interrupt vector management.