CVE-2026-97505 in Linux
Summary
by MITRE • 09/24/2026
In the Linux kernel, the following vulnerability has been resolved:
PCI/sysfs: Add CAP_SYS_ADMIN check to __resource_resize_store()
Currently, the __resource_resize_store() allows writing to the resourceN_resize sysfs attribute to change a BAR's size without checking for capabilities, currently relying only on the file access check.
Resizing a BAR modifies PCI device configuration and can disrupt active drivers. After the upcoming conversion to static attributes, it will also trigger resource file updates via sysfs_update_groups().
Add a CAP_SYS_ADMIN check to prevent unprivileged users from performing BAR resize operations.
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Analysis
by VulDB Data Team • 09/24/2026
The Linux kernel has addressed a significant security oversight within its PCI subsystem by implementing mandatory capability checks for the __resource_resize_store() function, which manages writes to the resourceN_resize sysfs attribute. This vulnerability stems from an insufficient access control mechanism that previously relied solely on standard file system permissions rather than validating specific user privileges. By allowing any process with write access to the corresponding device node to modify Base Address Register sizes without verifying administrative rights, the kernel exposed a critical attack vector where unprivileged users could alter hardware configuration parameters. This lack of privilege escalation protection represents a fundamental flaw in the principle of least privilege, as it permits low-privilege entities to perform operations that should be restricted to system administrators with CAP_SYS_ADMIN capabilities.
The technical nature of this vulnerability involves the manipulation of PCI device configuration space through sysfs interfaces. Base Address Registers define how memory-mapped I/O and memory regions are mapped for PCI devices, effectively controlling which physical addresses a device can access or expose to the operating system. When an unprivileged user modifies these registers via __resource_resize_store(), they directly alter the hardware's operational parameters without kernel-level validation of their authority to do so. This action bypasses standard security boundaries because sysfs attributes often inherit permissions from the underlying file system, which may be configured in ways that allow broader access than intended for sensitive device controls. The absence of a CAP_SYS_ADMIN check means that any user who can write to these specific files can trigger changes to hardware configuration, effectively granting them control over critical subsystem resources without proper authorization.
The operational impact of this vulnerability is severe and multifaceted, primarily centering on system stability and potential denial-of-service conditions. Resizing a BAR while drivers are actively using the associated memory regions or I/O ports can lead to immediate disruption of those drivers, causing application crashes, data corruption, or complete device malfunction. Furthermore, as noted in the resolution details, upcoming kernel conversions to static attributes will trigger resource file updates via sysfs_update_groups(), which could amplify the impact by automatically propagating these unauthorized changes across multiple system interfaces. An attacker exploiting this flaw could destabilize critical hardware components, leading to service outages or creating conditions for further exploitation if the altered configuration exposes sensitive memory regions to user-space applications. This disruption capability makes it a potent tool for local denial-of-service attacks against systems relying on PCI devices for essential operations.
From a classification perspective, this vulnerability aligns with CWE-269, which denotes Improper Privilege Management, as it fails to enforce appropriate access control levels before allowing sensitive configuration changes. It also relates to CWE-732, involving Incorrect Permission Assignment for Critical Resource, since the sysfs attribute was accessible to users who should not have had write privileges over hardware configuration parameters. In terms of adversary tactics, this flaw facilitates techniques associated with ATT&CK ID T1059, specifically command and script interpretation through system administration tools, or more broadly T1224, which covers file system manipulation for persistence or disruption. The vulnerability allows an attacker to leverage standard Linux utilities to interact directly with hardware interfaces, bypassing higher-level security controls that would normally restrict such low-level operations.
To mitigate this risk, the kernel developers have integrated a CAP_SYS_ADMIN check into __resource_resize_store(), ensuring that only processes with full system administration privileges can modify BAR sizes. This change enforces strict separation of duties by restricting hardware configuration changes to trusted administrative accounts. System administrators should verify that their sysfs permissions are configured correctly and avoid granting write access to device nodes unless absolutely necessary for specific operational requirements. Additionally, regular auditing of kernel updates is essential to ensure this patch is applied across all affected systems. Organizations relying on PCI devices for critical infrastructure must prioritize applying this update to prevent potential local privilege escalation or denial-of-service scenarios that could compromise system integrity and availability.