Linux Kernel Vulnerability in TUN Interface Affecting User Privileges

CVE-2026-52940

What is CVE-2026-52940?

A vulnerability in the Linux kernel's TUN interface allows unprivileged users to access uninitialized memory. Specifically, the function tun_put_user() fails to zero the entire vnet header structure, leading to the potential leakage of sensitive kernel stack data when reading non-tunnel packets. The issue primarily stems from inadequately initializing certain fields, which then expose stack memory to user space. The vulnerability is addressed by ensuring that the entire header is properly zeroed upon declaration, similar to existing safeguards in related functions.

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