Critical Information Leak in Linux Kernel - CVE-2025-40035
Summary
DEBIAN-CVE-2025-40035: In the Linux kernel, the following vulnerability has been resolved: Input: uinput - zero-initialize uinput_ff_upload_compat to avoid info leak Struct ff_effect_compat is embedded twice inside uinput_ff_upload_compat, con... 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 the Linux operating system, responsible for managing hardware resources and providing essential services to applications. It is widely used across various platforms, including servers, desktops, and embedded systems. The kernel's functionality includes process management, memory management, device drivers, and system calls. This vulnerability specifically affects the uinput subsystem, which allows user-space applications to create and handle input devices.
Vulnerability Detail
In the Linux kernel, a vulnerability identified as CVE-2025-40035 has been discovered in the uinput subsystem. This issue arises from the struct ff_effect_compat being embedded twice within uinput_ff_upload_compat, leading to internal padding and alignment issues. Specifically, there exists a hole after struct ff_replay, which, if not properly initialized, can result in the copy_to_user() function leaking sensitive stack data to user-space applications. This could potentially expose sensitive information and compromise system security.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a temporary workaround, users can manually initialize the ff_up_compat structure to zero before filling in valid fields. This can be done by adding the following code snippet in the relevant section of the kernel code:
memset(&ff_up_compat, 0, sizeof(ff_up_compat));
This will help mitigate the risk of information leakage until the system can be updated.
Conclusion
CVE-2025-40035 represents a significant security risk within the Linux kernel, specifically affecting the uinput subsystem. It is crucial for users to update their systems promptly to mitigate the risk of information leakage. Implementing the provided workaround can serve as a temporary measure until the system is fully patched.
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FAQ
CVE-2025-40035 is a vulnerability in the Linux kernel that can lead to information leakage due to improper initialization of a data structure in the uinput subsystem.
If exploited, this vulnerability could allow malicious user-space applications to access sensitive stack data, potentially compromising system security.
The vulnerability affects multiple versions of the Linux package across Debian ecosystems, including Debian 11, 12, 13, and 14.
You can use Vulert, a tool that monitors open-source vulnerabilities, to check if your application is affected by CVE-2025-40035. Visit Vulert Scanner to use the Vulert playground without any signup.
If an immediate update is not possible, consider implementing the provided workaround to mitigate the risk of information leakage until you can apply the necessary updates.
References
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