Divide-by-Zero Vulnerability in Linux Kernel's batman-adv Implementation

CVE-2026-63836

What is CVE-2026-63836?

In the Linux Kernel, a divide-by-zero vulnerability has been identified in the batman-adv networking module. Specifically, the problem arises in the tp_meter function, where improper arithmetic operations can lead to a critical runtime error. When the congestion window (cwnd) reaches the value of 0x20000000, mathematical operations in the function may produce a divide-by-zero scenario. This occurs due to incorrect unsigned 32-bit arithmetic assumptions, resulting in an overflow that can crash the kernel. The mathematical expressions should be refactored to ensure that these calculations avoid overflow and maintain precision, with constraints placed on the maximum segment size (MSS) to enhance system stability.

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