CVE-2024-49925 in Linux
Summary
by MITRE • 10/21/2024
In the Linux kernel, the following vulnerability has been resolved:
fbdev: efifb: Register sysfs groups through driver core
The driver core can register and cleanup sysfs groups already. Make use of that functionality to simplify the error handling and cleanup.
Also avoid a UAF race during unregistering where the sysctl attributes were usable after the info struct was freed.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 03/05/2026
The vulnerability identified as CVE-2024-49925 resides within the Linux kernel's framebuffer device subsystem, specifically affecting the efifb driver implementation. This issue represents a fundamental flaw in how sysfs groups are registered and managed within the driver core framework, creating potential security implications through improper resource handling and cleanup mechanisms. The efifb driver is responsible for managing framebuffer devices in EFI environments, making it a critical component in systems that rely on early boot graphics initialization and graphical user interfaces. The vulnerability stems from the driver's failure to properly leverage existing kernel infrastructure for sysfs group management, resulting in complex and error-prone manual handling of device attributes and their associated cleanup processes.
The technical flaw manifests in the driver's improper handling of sysfs group registration and cleanup operations, where the efifb driver attempts to manage these operations manually rather than utilizing the established driver core functionality. This approach creates a significant risk of use-after-free conditions during device unregistration, where sysctl attributes remain accessible even after the underlying information structure has been freed from memory. The vulnerability specifically targets the race condition that occurs during the unregistering process, where the driver core's cleanup mechanisms conflict with manual cleanup routines. This scenario creates a window where malicious actors could potentially exploit the dangling references to access freed memory structures, leading to unpredictable behavior or potential privilege escalation within the kernel space. The issue is classified as a use-after-free vulnerability that directly impacts the integrity of kernel memory management and device attribute handling.
The operational impact of this vulnerability extends beyond simple system instability, as it represents a potential pathway for privilege escalation and system compromise within kernel environments. When the efifb driver unregisters a framebuffer device, the improper cleanup mechanism leaves sysctl attributes accessible to userspace processes even after the associated kernel data structures have been deallocated. This condition creates opportunities for attackers to manipulate freed memory regions, potentially leading to information disclosure or arbitrary code execution in kernel context. The vulnerability affects systems running Linux kernels that implement the efifb driver, particularly those utilizing EFI firmware environments where framebuffer initialization occurs during early boot phases. The race condition during unregistering means that the window of vulnerability exists during device removal operations, making it particularly concerning for systems that frequently add or remove framebuffer devices or those with dynamic device management policies.
Mitigation strategies for CVE-2024-49925 focus on updating to patched kernel versions where the driver core's built-in sysfs group registration functionality is properly utilized. The fix involves modifying the efifb driver to delegate sysfs group registration and cleanup operations to the driver core, which provides robust error handling and proper synchronization mechanisms. This approach eliminates the manual cleanup routines that created the race condition and use-after-free scenarios. System administrators should prioritize kernel updates, particularly for production environments where EFI framebuffer devices are actively used. The solution aligns with security best practices outlined in the Linux kernel security guidelines and follows the principle of least privilege by ensuring proper resource management. Additionally, monitoring systems should be configured to detect unusual patterns in framebuffer device registration and unregistration activities, as these operations may indicate exploitation attempts. The vulnerability's resolution demonstrates the importance of leveraging established kernel infrastructure rather than implementing custom resource management routines, as the driver core provides well-tested and secure mechanisms for sysfs group handling. This fix also reinforces the broader security principle that kernel subsystems should minimize manual memory management operations to reduce the attack surface and prevent common vulnerabilities such as use-after-free conditions.