GHSA-QWCM-8GH9-XC6H

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-14 15:32
VLAI
Details

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

libceph: reject buckets with mismatched CRUSH ids

crush_decode() stores bucket data by array slot, and the mapper later derives the per-bucket workspace index from the decoded bucket id. A malformed map can therefore make one bucket reuse another bucket's workspace by encoding an id different from -1 - slot.

For uniform buckets, the second replica selection expands the source bucket's permutation into that aliased workspace buffer. If the source bucket is larger than the aliased bucket, the write runs past the smaller permutation array and can escape the kvmalloc'd CRUSH workspace. KASAN reports a slab OOB write of 4 bytes in bucket_perm_choose().

Reject buckets whose encoded id does not match their array slot. Valid CRUSH maps already use the canonical negative id corresponding to the bucket slot, so this restores the invariant expected by work->work[-1 - in->id] without changing valid map behavior.

Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-89656"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:19:51Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nlibceph: reject buckets with mismatched CRUSH ids\n\ncrush_decode() stores bucket data by array slot, and the mapper later\nderives the per-bucket workspace index from the decoded bucket id. A\nmalformed map can therefore make one bucket reuse another bucket\u0027s\nworkspace by encoding an id different from -1 - slot.\n\nFor uniform buckets, the second replica selection expands the source\nbucket\u0027s permutation into that aliased workspace buffer. If the source\nbucket is larger than the aliased bucket, the write runs past the smaller\npermutation array and can escape the kvmalloc\u0027d CRUSH workspace. KASAN\nreports a slab OOB write of 4 bytes in bucket_perm_choose().\n\nReject buckets whose encoded id does not match their array slot. Valid\nCRUSH maps already use the canonical negative id corresponding to the\nbucket slot, so this restores the invariant expected by\nwork-\u003ework[-1 - in-\u003eid] without changing valid map behavior.",
  "id": "GHSA-qwcm-8gh9-xc6h",
  "modified": "2026-09-14T15:32:33Z",
  "published": "2026-09-11T21:31:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89656"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/00562ccd4e88d092b9b851df50fad20442bfeb24"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3516a4131c4e45d62ee4e42e82c36930e8c1fbbd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3cde4a8302301679937474a5f7a851394cc1bd11"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4aeb93daadf388e72073abc204312dd364eeb30a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6e5c6ce252b1eccfd41670a5cf95ab44f7ba7022"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/79900d978158b2d80eef952fc41b9e4dc58d7b83"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/baad5875fdd2f5e248250fc3519bb045d64f1716"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ee59040d6ed1a5f8d10d27174b8f32c90ca8e89a"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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