Critical Vulnerability in Linux Kernel: Unconnected Socket Transport Assignment Issue
Summary
DEBIAN-CVE-2025-21854: In the Linux kernel, the following vulnerability has been resolved: sockmap, vsock: For connectible sockets allow only connected sockmap expects all vsocks to have a transport assigned, which is expressed in vsock_proto:... Affects linux versions < 6.12.17-1. Fixed in 6.12.17-1. How to fix ↓
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Background
The Linux kernel is a core component of many operating systems, providing essential services for hardware and software interaction. It is widely used in various environments, from servers to embedded systems. The kernel's networking stack includes support for virtual sockets (vsocks), which facilitate communication between virtual machines and host systems. However, a recent vulnerability has been identified that affects the handling of connectible sockets within the sockmap, potentially leading to system crashes.
Vulnerability Detail
In the Linux kernel, a vulnerability has been discovered in the handling of connectible sockets within the sockmap. The issue arises when an unconnected socket loses its assigned transport, which is not properly managed in the vsock/BPF receive path. This can lead to null pointer dereferences, causing system instability and crashes. Specifically, listening vsocks, which should not have any transport assigned, can inadvertently end up in a sockmap, leading to critical errors during operation. The vulnerability has been documented under the identifier DEBIAN-CVE-2025-21854.
How To Fix
Minimum fixed version
6.12.17-1
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 connectible sockets in the sockmap until the kernel is updated. This may involve modifying application logic to prevent the use of unconnected sockets in scenarios where they could be added to the sockmap.
Conclusion
The identified vulnerability in the Linux kernel poses significant risks to system stability due to improper handling of connectible sockets. Users are strongly advised to update to the patched version to mitigate these risks. Additionally, utilizing tools like Vulert can help monitor and manage vulnerabilities in open-source software effectively.
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FAQ
The vulnerability involves improper handling of connectible sockets in the Linux kernel's sockmap, leading to potential system crashes.
You can use the Vulert platform to monitor and alert for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected.
If exploited, this vulnerability can lead to null pointer dereferences, causing crashes and instability in systems running the affected kernel versions.
Yes, a patch has been released in version 6.12.17-1 of the Linux kernel for both Debian 13 and Debian 14.
If an immediate update is not possible, consider implementing the suggested workaround by avoiding the use of connectible sockets in the sockmap.
References
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