Kernel Vulnerability in Linux Affecting Atomic Fetch Operations

CVE-2026-43009

What is CVE-2026-43009?

A vulnerability exists in the Linux kernel impacting BPF atomic fetch operations. The issue arises when the backtrack_insn function encounters a BPF_STX instruction with BPF_ATOMIC and BPF_FETCH. In this scenario, the source register also acts as a destination, which can mistakenly lead to an incorrect state in the stack precision tracking. This flaw can allow the verifier's path pruning logic to erroneously treat divergent states as if they were equivalent, potentially affecting the execution flow and stability of applications relying on accurate memory management. A fix has been implemented to enhance the handling of these atomic fetch instructions, ensuring precision is correctly propagated to stack locations, prompting developers to update their systems to maintain security.

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