FKIE_CVE-2026-31413

Vulnerability from fkie_nvd - Published: 2026-04-12 06:16 - Updated: 2026-04-13 15:01
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix unsound scalar forking in maybe_fork_scalars() for BPF_OR maybe_fork_scalars() is called for both BPF_AND and BPF_OR when the source operand is a constant. When dst has signed range [-1, 0], it forks the verifier state: the pushed path gets dst = 0, the current path gets dst = -1. For BPF_AND this is correct: 0 & K == 0. For BPF_OR this is wrong: 0 | K == K, not 0. The pushed path therefore tracks dst as 0 when the runtime value is K, producing an exploitable verifier/runtime divergence that allows out-of-bounds map access. Fix this by passing env->insn_idx (instead of env->insn_idx + 1) to push_stack(), so the pushed path re-executes the ALU instruction with dst = 0 and naturally computes the correct result for any opcode.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/342aa1ee995ef5bbf876096dc3a5e51218d76fa4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/58bd87d0e69204dbd739e4387a1edb0c4b1644e7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c845894ebd6fb43226b3118d6b017942550910c5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d13281ae7ea8902b21d99d10a2c8caf0bdec0455
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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix unsound scalar forking in maybe_fork_scalars() for BPF_OR\n\nmaybe_fork_scalars() is called for both BPF_AND and BPF_OR when the\nsource operand is a constant.  When dst has signed range [-1, 0], it\nforks the verifier state: the pushed path gets dst = 0, the current\npath gets dst = -1.\n\nFor BPF_AND this is correct: 0 \u0026 K == 0.\nFor BPF_OR this is wrong:    0 | K == K, not 0.\n\nThe pushed path therefore tracks dst as 0 when the runtime value is K,\nproducing an exploitable verifier/runtime divergence that allows\nout-of-bounds map access.\n\nFix this by passing env-\u003einsn_idx (instead of env-\u003einsn_idx + 1) to\npush_stack(), so the pushed path re-executes the ALU instruction with\ndst = 0 and naturally computes the correct result for any opcode."
    }
  ],
  "id": "CVE-2026-31413",
  "lastModified": "2026-04-13T15:01:43.663",
  "metrics": {},
  "published": "2026-04-12T06:16:20.050",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/342aa1ee995ef5bbf876096dc3a5e51218d76fa4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/58bd87d0e69204dbd739e4387a1edb0c4b1644e7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c845894ebd6fb43226b3118d6b017942550910c5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d13281ae7ea8902b21d99d10a2c8caf0bdec0455"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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