Critical SCTP Vulnerability in Linux Kernel: Null Pointer Dereference Risk
Summary
CVE-2025-21636: In the Linux kernel, the following vulnerability has been resolved: sctp: sysctl: plpmtud_probe_interval: avoid using current->nsproxy As mentioned in a previous commit of this series, using the 'net' structure via 'curr... Affects linux versions < 6.1.128-1. Fixed in 6.1.128-1. How to fix ↓
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Background
The Linux kernel is the core component of a Linux operating system, responsible for managing hardware resources and providing essential services to software applications. It supports various functionalities including process management, memory management, device drivers, and system calls. The kernel is crucial for system stability and security, making it imperative to address vulnerabilities that may compromise its integrity.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified in the SCTP (Stream Control Transmission Protocol) subsystem related to the sysctl interface. The issue arises from the use of 'current->nsproxy' to access the 'net' structure, which can lead to inconsistencies and potential null pointer dereferences. Specifically, if the current task is exiting, 'current->nsproxy' may be NULL, resulting in a crash (Oops) when attempting to dereference it. This vulnerability could be exploited to cause system instability or denial of service, making it critical to address.
How To Fix
Minimum fixed version
6.1.128-1
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
As a temporary workaround, users can avoid using the 'current->nsproxy' structure directly and instead utilize the 'net' structure obtained from 'table->data' using the 'container_of()' macro. This change can help mitigate the risk until a full update is applied.
Conclusion
The CVE-2025-21636 vulnerability in the Linux kernel poses a significant risk due to potential null pointer dereferences. It is crucial for users to update their systems to the latest patched version to mitigate this risk. Utilizing tools like Vulert can help monitor for such vulnerabilities effectively.
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FAQ
CVE-2025-21636 is a vulnerability in the Linux kernel's SCTP subsystem that can lead to a null pointer dereference, potentially causing system crashes.
You can use Vulert to monitor and alert for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected by this vulnerability.
The primary risk is system instability or denial of service due to potential crashes when the vulnerability is exploited.
Yes, a patch is available. Users should update their Linux kernel to the latest version that includes the fix for CVE-2025-21636.
As a temporary measure, avoid using the 'current->nsproxy' structure and utilize the 'net' structure from 'table->data' instead.
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