UDP GSO Fraglist Segmentation Vulnerability in Linux Kernel
Summary
CVE-2025-38124: In the Linux kernel, the following vulnerability has been resolved: net: fix udp gso skb_segment after pull from frag_list Commit a1e40ac5b5e9 ("net: gso: fix udp gso fraglist segmentation after pull from frag_list") det... Affects linux versions < 6.1.147-1. Fixed in 6.1.147-1. How to fix ↓
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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 robustness, flexibility, and extensive support for various hardware architectures. However, vulnerabilities can arise due to complex interactions within its networking stack, particularly in the handling of Generic Segmentation Offload (GSO) for UDP packets. This specific vulnerability affects the segmentation of packets that utilize fraglist, which can lead to unexpected behavior and potential system crashes.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified in the handling of UDP GSO fraglist segmentation. The issue arises when packets with modified geometry are processed, leading to invalid conditions that can trigger exceptions during the segmentation process. This vulnerability is rooted in the complex skb_segment code, which is responsible for segmenting packets. If the fraglist payload is partially pulled into the head_skb, it violates the expected structure of SKB_GSO_FRAGLIST, resulting in potential kernel crashes and instability. The vulnerability is particularly concerning as it can be exploited through optional datapath hooks such as NAT and BPF, which may inadvertently modify fraglist skbs.
How To Fix
Minimum fixed version
6.1.147-1
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 optional datapath hooks that modify fraglist skbs until the kernel is updated. This may help mitigate the risk of triggering the vulnerability while a permanent fix is being implemented.
Conclusion
The UDP GSO fraglist segmentation vulnerability in the Linux kernel poses significant risks to system stability and performance. It is crucial for users to update their kernel to the latest patched version to mitigate these risks. Utilizing tools like Vulert can help monitor for such vulnerabilities in real-time, ensuring that systems remain secure.
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FAQ
The vulnerability can lead to kernel crashes and system instability when processing certain UDP packets, potentially affecting network performance.
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 by this vulnerability without any signup.
The vulnerability affects all versions of the Linux kernel prior to the patch that addresses this specific issue.
While the primary risk is system instability and crashes, there is a potential for data loss if the system crashes during critical operations.
If an immediate update is not possible, consider implementing the suggested workaround by avoiding the use of optional datapath hooks that may modify fraglist skbs.
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