Graceful Framebuffer Removal Vulnerability in Linux Kernel
Summary
CVE-2025-21976: In the Linux kernel, the following vulnerability has been resolved: fbdev: hyperv_fb: Allow graceful removal of framebuffer When a Hyper-V framebuffer device is unbind, hyperv_fb driver tries to release the framebuffer f... 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 Linux operating systems, managing hardware and system resources. It provides essential services for all other parts of the system, including device drivers, system calls, and process management. The kernel's framebuffer subsystem allows for the management of graphical output to display devices. This vulnerability specifically affects the Hyper-V framebuffer driver, which is used in virtualized environments to manage graphics output.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified in the hyperv_fb driver related to the framebuffer's removal process. When a Hyper-V framebuffer device is unbound, the driver attempts to forcefully release the framebuffer. If the framebuffer is still in use, this leads to a warning message and prevents the framebuffer from being released properly. This can result in resource leaks and potential instability in the system, as the framebuffer remains allocated even when it is no longer needed.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
Currently, no specific workarounds are provided for this vulnerability. However, users can avoid unbinding the framebuffer device while it is still in use to prevent the warning and resource leak.
Conclusion
The vulnerability CVE-2025-21976 in the Linux kernel's hyperv_fb driver poses a risk of resource leaks and system instability due to improper framebuffer removal. Users are advised to update their kernel to the patched version to mitigate this issue. Monitoring tools like Vulert can help in identifying vulnerabilities in your software.
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FAQ
The vulnerability can lead to resource leaks and system instability, as the framebuffer may not be released properly when unbound.
You can use the Vulert platform to monitor and alert for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected.
Yes, a patch is available in the form of an updated kernel version. For Debian 13, the fixed version is 6.12.20-1.
While there are no specific workarounds, you should avoid unbinding the framebuffer device while it is still in use to mitigate the issue temporarily.
You can find detailed information about this vulnerability in the CVE database or by visiting the official Linux kernel documentation.
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