Critical Vulnerability in Linux Kernel: vmxnet3 Malformed Packet Handling
Summary
DEBIAN-CVE-2025-37799: In the Linux kernel, the following vulnerability has been resolved: vmxnet3: Fix malformed packet sizing in vmxnet3_process_xdp vmxnet3 driver's XDP handling is buggy for packet sizes using ring0 (that is, packet sizes b... Affects linux versions < 6.12.27-1. Fixed in 6.12.27-1. How to fix ↓
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Background
The Linux kernel is a core component of the operating system that manages hardware and system resources. It provides essential services for all other parts of the system, including device drivers, system calls, and process management. The vmxnet3 driver is a paravirtualized network driver designed for high-performance virtualized environments. This driver is crucial for ensuring efficient network communication in virtual machines. However, it has been found to have a vulnerability that affects its handling of packet sizes, potentially leading to data leakage and connectivity issues.
Vulnerability Detail
The vulnerability arises from a bug in the vmxnet3 driver's XDP (eXpress Data Path) handling, specifically for packet sizes between 128 bytes and 3k bytes. This flaw can lead to malformed packets being sent over the network, where uninitialized kernel data may be leaked. For instance, packets that should be 152 bytes in size were found to be 1482 bytes, containing extraneous data from previous packets. This issue can cause connectivity problems, particularly when the MTU (Maximum Transmission Unit) settings are not aligned between the XDP load balancer and the backend node, leading to dropped requests and potential data exposure.
How To Fix
Minimum fixed version
6.12.27-1
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 lower the MTU on the XDP load balancer to a value such as 1480. This adjustment may help mitigate the issue by allowing packets to be processed without exceeding the MTU limit, thus preventing dropped requests.
Conclusion
The vulnerability in the Linux kernel's vmxnet3 driver poses significant risks related to malformed packet handling, which can lead to data leakage and connectivity issues. Users are advised to update to the patched version to mitigate these risks. Temporary workarounds are available, but a permanent fix is recommended for long-term security.
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FAQ
The vmxnet3 driver is a paravirtualized network driver used in virtualized environments to enhance network performance.
The risks include potential data leakage, connectivity issues, and the possibility of uninitialized kernel data being sent over the network.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
Yes, the permanent fix is to update the Linux package to version 6.12.27-1 or later.
If an immediate update is not possible, consider lowering the MTU on the XDP load balancer as a temporary workaround.
References
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