GHSA-JVQ3-FGQ9-MFPJ

Vulnerability from github – Published: 2026-04-22 15:31 – Updated: 2026-04-27 15:30
VLAI?
Details

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().

Severity ?
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-31525"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-787"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-04-22T14:16:52Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix undefined behavior in interpreter sdiv/smod for INT_MIN\n\nThe BPF interpreter\u0027s signed 32-bit division and modulo handlers use\nthe kernel abs() macro on s32 operands. The abs() macro documentation\n(include/linux/math.h) explicitly states the result is undefined when\nthe input is the type minimum. When DST contains S32_MIN (0x80000000),\nabs((s32)DST) triggers undefined behavior and returns S32_MIN unchanged\non arm64/x86. This value is then sign-extended to u64 as\n0xFFFFFFFF80000000, causing do_div() to compute the wrong result.\n\nThe verifier\u0027s abstract interpretation (scalar32_min_max_sdiv) computes\nthe mathematically correct result for range tracking, creating a\nverifier/interpreter mismatch that can be exploited for out-of-bounds\nmap value access.\n\nIntroduce abs_s32() which handles S32_MIN correctly by casting to u32\nbefore negating, avoiding signed overflow entirely. Replace all 8\nabs((s32)...) call sites in the interpreter\u0027s sdiv32/smod32 handlers.\n\ns32 is the only affected case -- the s64 division/modulo handlers do\nnot use abs().",
  "id": "GHSA-jvq3-fgq9-mfpj",
  "modified": "2026-04-27T15:30:40Z",
  "published": "2026-04-22T15:31:44Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31525"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0d5d8c3ce45c734aaf3c51cbef59155a6746157d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/694ea55f1b1c74f9942d91ec366ae9e822422e42"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9ab1227765c446942f290c83382f0b19887c55cf"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c77b30bd1dcb61f66c640ff7d2757816210c7cb0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f14ca604c0ff274fba19f73f1f0485c0047c1396"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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