Critical TOCTOU Race Condition in Linux Kernel's Rainshadow-CEC Package
Summary
CVE-2025-39713: In the Linux kernel, the following vulnerability has been resolved: media: rainshadow-cec: fix TOCTOU race condition in rain_interrupt() In the interrupt handler rain_interrupt(), the buffer full check on rain->buf_len i... 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, providing essential services for hardware management and system resources. The rainshadow-cec module is responsible for handling CEC (Consumer Electronics Control) communications, allowing devices to control each other over HDMI. This module is crucial for ensuring seamless interactions between devices, but it is susceptible to vulnerabilities that can compromise system stability and security.
Vulnerability Detail
In the Linux kernel, a Time-of-Check to Time-of-Use (TOCTOU) race condition has been identified in the rainshadow-cec module's interrupt handler, rain_interrupt(). The vulnerability arises because the check for a full buffer (rain->buf_len) occurs before acquiring the necessary lock (rain->buf_lock). This oversight allows multiple interrupt invocations to race, potentially leading to a buffer overflow as concurrent accesses modify buf_len. If exploited, this could result in data corruption or system crashes.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
Currently, there are no specific workarounds mentioned for this vulnerability. The best course of action is to apply the patch as soon as it becomes available.
Conclusion
The identified TOCTOU race condition in the Linux kernel's rainshadow-cec module poses significant risks, including potential buffer overflows and system instability. Users are strongly advised to update their systems to the latest patched version to mitigate these risks. Utilizing tools like Vulert can enhance your ability to monitor and respond to vulnerabilities effectively.
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FAQ
A TOCTOU race condition occurs when a system checks a condition (like buffer length) and then uses that condition later, without ensuring that the condition hasn't changed in the meantime, leading to potential vulnerabilities.
You can use Vulert, which monitors and alerts for open-source vulnerabilities in your software. By simply using a manifest file like package-lock.json, you can check if your application is affected by this vulnerability.
Exploiting this vulnerability could lead to buffer overflows, resulting in data corruption, system crashes, or unauthorized access to system resources.
Yes, all versions of the Linux kernel that include the rainshadow-cec module prior to the patch are vulnerable to this issue.
You can use tools like Vulert to receive real-time alerts for open-source vulnerabilities, ensuring that you are always informed about potential risks.
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