CVE-2026-31525
bpf: Fix undefined behavior in interpreter sdiv/smod for INT_MIN
Description
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().
INFO
Published Date :
April 22, 2026, 2:16 p.m.
Last Modified :
April 22, 2026, 2:16 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Apply the provided kernel patch.
- Update the Linux kernel to a fixed version.
- Replace abs() with abs_s32() in interpreter.
- Verify s32 division/modulo handlers.
References to Advisories, Solutions, and Tools
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CVE-2026-31525.
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associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
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approaches employed by adversaries to exploit the CVE-2026-31525
weaknesses.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Apr. 22, 2026
Action Type Old Value New Value Added Description 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(). Added Reference https://git.kernel.org/stable/c/0d5d8c3ce45c734aaf3c51cbef59155a6746157d Added Reference https://git.kernel.org/stable/c/694ea55f1b1c74f9942d91ec366ae9e822422e42 Added Reference https://git.kernel.org/stable/c/9ab1227765c446942f290c83382f0b19887c55cf Added Reference https://git.kernel.org/stable/c/c77b30bd1dcb61f66c640ff7d2757816210c7cb0 Added Reference https://git.kernel.org/stable/c/f14ca604c0ff274fba19f73f1f0485c0047c1396