TX Path Vulnerability in Linux Kernel: Unreadable SKBs in Debian Packages
Summary
DEBIAN-CVE-2025-21954: In the Linux kernel, the following vulnerability has been resolved: netmem: prevent TX of unreadable skbs Currently on stable trees we have support for netmem/devmem RX but not TX. Affects linux versions < 6.12.20-1. Fixed in 6.12.20-1. How to fix ↓
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Background
The Linux kernel is a core component of the Debian operating system, responsible for managing hardware resources and providing essential services to software applications. It supports various functionalities, including process management, memory management, and device control. The kernel is crucial for system stability and performance, making its security paramount. This vulnerability specifically affects the handling of socket buffers (skbs) in the transmission (TX) path, which can lead to unsafe operations if unreadable packets are processed.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified that allows the transmission of unreadable socket buffers (skbs) through the device's TX path. This issue arises from the lack of support for netmem/devmem TX, which can lead to unsafe forwarding of RX unreadable packets. If exploited, this vulnerability could allow a device to call DMA-mapping APIs on addresses that should not be accessed, potentially leading to system instability or data corruption.
How To Fix
Minimum fixed version
6.12.20-1
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, it is advisable to avoid configurations that may lead to the transmission of unreadable skbs until the package is updated.
Conclusion
The vulnerability in the Linux kernel regarding unreadable skbs poses a significant risk to systems running Debian 13 and 14. It is crucial to update to the patched version 6.12.20-1 to mitigate this risk. Regular monitoring and prompt updates are essential for maintaining system security.
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FAQ
An unreadable skb (socket buffer) is a data structure used in the Linux kernel that cannot be processed correctly due to memory access issues.
This vulnerability can lead to unsafe operations in the TX path of the network device, potentially causing system instability or data corruption.
If you are using Debian 13 or 14 with a Linux version prior to 6.12.20-1, your system is vulnerable. You can check your package version using 'dpkg -l | grep linux'.
You can use Vulert, which monitors and alerts for open-source vulnerabilities in your software using a manifest file like package-lock.json. Visit https://vulert.com for more information.
While there are no specific workarounds, it is recommended to avoid configurations that may lead to the transmission of unreadable skbs until you can apply the update.
References
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