CVE-2021-47597: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-47597 is a kernel information leak vulnerability in the Linux kernel's inetdiag subsystem. The vulnerability was discovered in December 2021 and specifically affects UDP sockets. The issue occurs when UDP was not initializing r->idiagexpires in the inetskdiag_fill() function, which could lead to uninitialized kernel memory being exposed to unprivileged users (Kernel Commit).

The vulnerability exists in the inetdiagfill() function where the idiagexpires field was left uninitialized for UDP sockets. When this uninitialized data is copied to userspace through netlink messages, it could expose 4 bytes (bytes 68-71) of kernel memory. The issue was detected by the Kernel Memory Sanitizer (KMSAN) which reported the kernel-infoleak in the instrumentcopytouser function (Kernel Commit).

This vulnerability allows unprivileged local users to read uninitialized kernel memory, potentially exposing sensitive information. The exposure is limited to specific memory regions related to network socket structures (Kernel Commit).

The vulnerability was fixed by initializing the idiagexpires field to 0 at the beginning of the inetskdiagfill() function. The fix was implemented in the Linux kernel through commit 71ddeac8cd1d217744a0e060ff520e147c9328d1 and backported to various stable kernel versions (Kernel Commit).