CVE-2026-99257 in Linux
Summary
by MITRE • 11/03/2026
In the Linux kernel, the following vulnerability has been resolved:
gpio: shared: gracefully handle no-device lookup of shared GPIOs
We use platform lookup tables for shared GPIOs. This mechanism needs a struct device to work so fwnode-based lookup with no device associated currently causes a NULL-pointer deference.
Adding this functionality will require a larger rework and it has never worked anyway so add a check that allows the kernel to gracefully handle this situation with an error ahead of implementing that functionality as a new feature.
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Analysis
by VulDB Data Team • 11/03/2026
The Linux kernel GPIO subsystem relies on platform lookup tables to manage shared General Purpose Input/Output resources, ensuring that multiple drivers can safely access hardware lines without conflict. A critical flaw exists in the mechanism used for firmware node-based lookups when no associated device structure is present during initialization or runtime operations. Specifically, the code path assumes the existence of a valid struct device pointer to facilitate the lookup process. When this assumption fails and a NULL pointer is passed due to the absence of an associated device context, the kernel attempts to dereference this invalid memory address. This results in a NULL-pointer dereference vulnerability, which typically manifests as a kernel panic or system crash, effectively causing a denial of service for the affected system instance.
From a technical perspective, this flaw represents a classic input validation error where the software fails to verify that required data structures are initialized and valid before use. In terms of industry standards, this aligns with CWE-476, which describes NULL Pointer Dereference vulnerabilities. The root cause lies in the lack of defensive programming practices within the GPIO shared resource handling logic. While fwnode-based lookups are designed to support device-independent configurations, the current implementation incorrectly propagates a null reference when such independence is attempted without proper fallback mechanisms or context establishment. This oversight allows an attacker who can trigger this specific code path through local system interactions or potentially via remote triggers if exposed by other subsystems to induce instability in the kernel space.
The operational impact of this vulnerability is primarily centered on system reliability and availability. A successful exploitation leads to a crash of the operating system, requiring a reboot to restore service. This disrupts critical operations running on the affected Linux distribution or embedded device. Although the immediate effect is a denial of service, such crashes can also mask other security issues by clearing memory states unexpectedly or preventing further execution of security-critical checks that might have been scheduled after the crash point. For systems relying on high availability, this represents a significant risk to uptime and operational continuity.
Mitigation strategies involve applying the upstream kernel patch that introduces explicit NULL pointer checks before attempting device-based lookups for shared GPIOs. This change ensures that if no device is associated with the firmware node lookup request, the function returns an appropriate error code rather than proceeding to dereference a null address. Administrators should update their Linux kernels to versions where this fix has been integrated. Additionally, developers integrating custom drivers or modifying GPIO subsystem behavior should ensure they provide valid device contexts for all shared resource requests or implement robust error handling paths that do not assume the presence of specific kernel structures unless explicitly verified. This aligns with secure coding guidelines emphasizing defensive programming and rigorous input validation to prevent memory corruption errors in core system components.