BPF Helper Function Vulnerability in Linux Kernel by The Linux Foundation

CVE-2025-39990

What is CVE-2025-39990?

A vulnerability has been identified in the Linux kernel related to the BPF helper function, specifically in its validation process. The issue arises when the helper function pointer may be NULL due to a disabled configuration option. The kernel's verifier reported a bug where this lack of validation could lead to unintended behavior. The implementation has been refined to check the helper function directly in 'get_helper_proto' and to mark the tail_call helper function with 'BPF_PTR_POISON' to prevent misuse, as it is deliberately not used.

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