Out-of-Bounds Write Vulnerability in Linux Kernel's fbdev Package
Summary
CVE-2025-38685: In the Linux kernel, the following vulnerability has been resolved: fbdev: Fix vmalloc out-of-bounds write in fast_imageblit This issue triggers when a userspace program does an ioctl FBIOPUT_CON2FBMAP by passing console... Affects linux versions 5.10.103-1 – 6.9.9-1. No fix is published. How to fix ↓
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Background
The Linux kernel is the core component of many operating systems, responsible for managing hardware and system resources. The fbdev subsystem is specifically designed for handling frame buffers, allowing graphical output to be rendered on screens. This subsystem is crucial for graphical user interfaces and applications that require direct access to the display. However, vulnerabilities within this subsystem can lead to severe security risks, including unauthorized access and system crashes.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified in the fbdev subsystem that allows for an out-of-bounds write during the execution of the FBIOPUT_CON2FBMAP ioctl. This occurs when a userspace program attempts to map a console to a frame buffer. If the resizing of the console fails, the system continues to process the mapping, leading to potential memory corruption and exploitation. This vulnerability can be exploited by attackers to manipulate memory, potentially leading to arbitrary code execution or system instability.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a temporary workaround, avoid using the FBIOPUT_CON2FBMAP ioctl until the package is updated. This can help mitigate the risk of exploitation until a patch is applied.
Conclusion
The out-of-bounds write vulnerability in the Linux kernel's fbdev subsystem poses significant security risks. It is crucial for users to update their systems to the patched versions to mitigate these risks. Temporary workarounds can help reduce exposure until updates are applied.
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FAQ
FBIOPUT_CON2FBMAP is an ioctl command used to map a console to a frame buffer in the Linux kernel's fbdev subsystem.
An attacker can exploit this vulnerability by sending crafted requests to the ioctl, leading to memory corruption and potential arbitrary code execution.
The vulnerability affects various Debian versions, specifically Debian 11, 12, 13, and 14, where the Linux kernel is utilized.
Yes, you can use Vulert, which monitors open-source vulnerabilities in your software using a manifest file like package-lock.json. You can check if your application is affected by this vulnerability using the Vulert playground without any signup.
If immediate updates are not possible, refrain from using the affected ioctl command as a temporary measure to reduce the risk of exploitation.
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