Critical Lockdown Check Bypass in Linux Kernel - CVE-2025-40021
Summary
DEBIAN-CVE-2025-40021: In the Linux kernel, the following vulnerability has been resolved: tracing: dynevent: Add a missing lockdown check on dynevent Since dynamic_events interface on tracefs is compatible with kprobe_events and uprobe_events... Affects linux versions 5.10.103-1 – 6.9.9-1. No fix is published. How to fix ↓
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Background
The Linux kernel is the core component of many operating systems, providing essential services for hardware and software interaction. It is known for its stability, performance, and security features. However, like any complex software, it can have vulnerabilities. This specific issue relates to the dynamic_events interface on tracefs, which is used for tracing events in the kernel. The vulnerability arises from a missing lockdown check, potentially allowing unauthorized access to sensitive tracing functionalities.
Vulnerability Detail
In the Linux kernel, a vulnerability identified as CVE-2025-40021 has been discovered in the tracing subsystem. The dynamic_events interface on tracefs, which is compatible with kprobe_events and uprobe_events, lacks a proper lockdown check. This oversight means that if the lockdown status is set, the system does not reject unauthorized access attempts, leading to potential exploitation. Attackers could leverage this flaw to manipulate kernel tracing events, which could compromise system integrity and security.
How To Fix
No fixed version is published for this vulnerability.
Tip — Not sure whether your app is affected? Vulert can check the versions your app actually runs. Scan free →
Workaround
As a temporary workaround, users can restrict access to the dynamic_events interface on tracefs by modifying permissions or disabling the tracing functionality until the kernel is updated. This can be done by executing: sudo chmod 700 /sys/kernel/debug/tracing/dynamic_events.
Conclusion
The CVE-2025-40021 vulnerability in the Linux kernel poses a significant risk due to its potential to allow unauthorized access to tracing functionalities. It is crucial for users to update their systems to the patched version to mitigate this risk. Additionally, utilizing tools like Vulert can help monitor and manage vulnerabilities effectively.
See every vulnerability recorded for linux →
FAQ
CVE-2025-40021 is a vulnerability in the Linux kernel that allows unauthorized access to the dynamic_events interface due to a missing lockdown check.
If exploited, this vulnerability could allow attackers to manipulate kernel tracing events, potentially compromising system integrity and security.
The vulnerability affects various Debian versions, including Debian 11, 12, 13, and 14, specifically in the Linux kernel package.
You can use Vulert, which monitors and alerts for open-source vulnerabilities in your software. By using the Vulert playground, you can check if your application is affected without any signup.
If an immediate update is not possible, consider applying the suggested workaround to restrict access to the dynamic_events interface until you can perform the update.
References
Related vulnerabilities
Recent vulnerabilities recorded for linux.
