CVE-2025-21791

Summary

CVE-2025-21791 is a vulnerability affecting the Linux kernel. In the function l3mdev_l3_out(), RCU (Read-Copy-Update) protection was not being used properly. This issue allowed certain functions such as raw_sendmsg(), ip_push_pending_frames(), ip_send_skb(), ip_local_out(), and __ip_local_out() to be called without RCU being held. Consequently, a Use-After-Free (UAF) condition could arise. To mitigate this vulnerability, developers added rcu_read_lock() and rcu_read_unlock() pair to the relevant code sections to ensure RCU protection is maintained during the execution of these functions.

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