CVE-2026-31525

About vulnerability

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix undefined behavior in interpreter sdiv/smod for INT_MIN The BPF interpreter’s signed 32-bit division and modulo handlers use the kernel abs() macro on s32 operands. The abs() macro documentation (include/linux/math.h) explicitly states the result is undefined when the input is the type minimum. When DST contains S32_MIN (0x80000000), abs((s32)DST) triggers undefined behavior and returns S32_MIN unchanged on arm64/x86. This value is then sign-extended to u64 as 0xFFFFFFFF80000000, causing do_div() to compute the wrong result. The verifier’s abstract interpretation (scalar32_min_max_sdiv) computes the mathematically correct result for range tracking, creating a verifier/interpreter mismatch that can be exploited for out-of-bounds map value access. Introduce abs_s32() which handles S32_MIN correctly by casting to u32 before negating, avoiding signed overflow entirely. Replace all 8 abs((s32)…) call sites in the interpreter’s sdiv32/smod32 handlers. s32 is the only affected case – the s64 division/modulo handlers do not use abs(). A flaw was found in the Linux kernel’s Berkeley Packet Filter (BPF) interpreter. The interpreter’s signed 32-bit division and modulo operations exhibit undefined behavior when processing the minimum 32-bit signed integer value (S32_MIN) due to an incorrect use of the abs() macro. This inconsistency between the interpreter’s execution and the verifier’s expected behavior can be leveraged by a local attacker. Successful exploitation could lead to out-of-bounds memory access within BPF maps, potentially resulting in information disclosure or privilege escalation.

Live-patch status from KernelCare for each operating system.