ghsa-pfch-hqrr-v4q4
Vulnerability from github
Published
2025-11-12 12:30
Modified
2025-11-12 12:30
Details

In the Linux kernel, the following vulnerability has been resolved:

bpf: Reject negative offsets for ALU ops

When verifying BPF programs, the check_alu_op() function validates instructions with ALU operations. The 'offset' field in these instructions is a signed 16-bit integer.

The existing check 'insn->off > 1' was intended to ensure the offset is either 0, or 1 for BPF_MOD/BPF_DIV. However, because 'insn->off' is signed, this check incorrectly accepts all negative values (e.g., -1).

This commit tightens the validation by changing the condition to '(insn->off != 0 && insn->off != 1)'. This ensures that any value other than the explicitly permitted 0 and 1 is rejected, hardening the verifier against malformed BPF programs.

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{
  "affected": [],
  "aliases": [
    "CVE-2025-40169"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-11-12T11:15:47Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject negative offsets for ALU ops\n\nWhen verifying BPF programs, the check_alu_op() function validates\ninstructions with ALU operations. The \u0027offset\u0027 field in these\ninstructions is a signed 16-bit integer.\n\nThe existing check \u0027insn-\u003eoff \u003e 1\u0027 was intended to ensure the offset is\neither 0, or 1 for BPF_MOD/BPF_DIV. However, because \u0027insn-\u003eoff\u0027 is\nsigned, this check incorrectly accepts all negative values (e.g., -1).\n\nThis commit tightens the validation by changing the condition to\n\u0027(insn-\u003eoff != 0 \u0026\u0026 insn-\u003eoff != 1)\u0027. This ensures that any value\nother than the explicitly permitted 0 and 1 is rejected, hardening the\nverifier against malformed BPF programs.",
  "id": "GHSA-pfch-hqrr-v4q4",
  "modified": "2025-11-12T12:30:28Z",
  "published": "2025-11-12T12:30:28Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-40169"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/21167bf70dbe400563e189ac632258d35eda38b5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3bce44b344040e5eef3d64d38b157c15304c0aab"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5017c302ca4b2a45149ad64e058fa2d5623c068f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/55c0ced59fe17dee34e9dfd5f7be63cbab207758"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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