Null Pointer Dereference Vulnerability in Linux Kernel - CVE-2025-37953
Summary
CVE-2025-37953: In the Linux kernel, the following vulnerability has been resolved: sch_htb: make htb_deactivate() idempotent Alan reported a NULL pointer dereference in htb_next_rb_node() after we made htb_qlen_notify() idempotent. Affects linux versions < 6.1.140-1. Fixed in 6.1.140-1. 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. It provides essential services for all other parts of the operating system. This vulnerability affects the 'linux' package in Debian versions 12 and 13, which is crucial for system stability and performance. The specific issue arises from the handling of the Hierarchical Token Bucket (HTB) queuing discipline, which is used for traffic control in networking.
Vulnerability Detail
In the Linux kernel, a NULL pointer dereference vulnerability has been identified in the htb_next_rb_node() function. This issue was reported following the implementation of idempotency in the htb_qlen_notify() function. The vulnerability occurs when htb_deactivate() is called multiple times, leading to a situation where the clprio[prio]->ptr may be set to NULL. This can result in a system crash or unexpected behavior when htb_next_rb_node() is invoked with a NULL pointer. The regression introduced by this change can compromise the stability of the kernel, affecting network traffic management.
How To Fix
Minimum fixed version
6.1.140-1
This is the first release that contains the fix.
sudo apt-get install --only-upgrade linuxTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
Currently, there are no specific workarounds mentioned for this vulnerability. However, users are advised to avoid configurations that may lead to multiple calls to htb_deactivate() until the patch is applied.
Conclusion
The CVE-2025-37953 vulnerability in the Linux kernel poses a significant risk due to its potential to cause system instability through NULL pointer dereference. It is crucial for users to update their systems to the patched versions of the Linux kernel to mitigate this risk. Utilizing tools like Vulert can further enhance security by providing real-time monitoring for vulnerabilities.
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FAQ
CVE-2025-37953 is a vulnerability in the Linux kernel that can lead to a NULL pointer dereference, potentially causing system crashes.
The vulnerability affects the Linux kernel in Debian versions 12 and 13.
You can use tools like Vulert to monitor and alert for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected.
While there are no specific workarounds, it is advisable to avoid configurations that may trigger the vulnerability until a patch is applied.
Vulert monitors open-source vulnerabilities in real-time using a manifest file like package-lock.json, providing alerts without requiring code access or installation.
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