Linux Kernel BPF Range Refinement Vulnerability in Networking

CVE-2025-39748

What is CVE-2025-39748?

A vulnerability in the Linux kernel's BPF implementation has been identified where the verifier fails to appropriately refine register bounds after JSET instructions. This can lead to inconsistencies in register states, as paths deemed unreachable at runtime are explored incorrectly, creating potential security risks. The issue was reported by Syzbot and pertains to specific BPF program instruction sets that generate misleading range validations. A fix has been implemented to forget these ranges, enhancing the robustness of the kernel's verifier.

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