{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-46124",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-46124"
  ],
  "published": "2026-05-28T09:36:53Z",
  "summary": "isofs: validate block number from NFS file handle in isofs_export_iget",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nisofs: validate block number from NFS file handle in isofs_export_iget\n\nisofs_fh_to_dentry() and isofs_fh_to_parent() pass an attacker-\ncontrolled block number (ifid->block or ifid->parent_block) from\nthe NFS file handle to isofs_export_iget(), which only rejects\nblock == 0 before calling isofs_iget() and ultimately sb_bread().\nA crafted file handle with fh_len sufficient to pass the check\nadded by commit 0405d4b63d08 (\"isofs: Prevent the use of too small\nfid\") can still drive the server to read any in-range block on the\nbacking device as if it were an iso_directory_record.  That earlier\nfix was assigned CVE-2025-37780.\n\nsb_bread() on an out-of-range block returns NULL cleanly via the\nEIO path, so there is no memory-safety violation.  For in-range\nreads of adjacent-partition data on the same block device, the\nunrelated bytes end up in iso_inode_info fields that reach the NFS\nclient as dentry metadata.  The deployment surface (isofs exported\nover NFS from loop-mounted images) is narrow and requires an\nauthenticated NFS peer, but the malformed-file-handle class is\nreportable as hardening next to the existing CVE-2025-37780 fix.\n\nReject block >= ISOFS_SB(sb)->s_nzones in isofs_export_iget() so\nthe check covers both isofs_fh_to_dentry() and isofs_fh_to_parent()\ncall sites with a single line.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"
    }
  ],
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-46124"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ee0024f5a7e3c73aa253869fae9650ae054093ca"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/31dbb4ba0f719ae7774e4c0c95172c9bf81692f5"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/908a76f0b1038035e6ebb4f2293ce079f92e0a02"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/bb0988ed4f2e26d59bbb58f644cb3a55b7521e21"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/0a1af74ae2177bda3aee0837a0546309aa539d0d"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/afbafeddf23db13fe2edb2d5c0bf4bbb13d7881b"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/4c721a1d9b3c4fcaf59cc9b2281e3ec5a043e1a6"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/24376458138387fb251e782e624c7776e9826796"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T13:16:28Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.5,
      "cvss_v3_severity": "High",
      "scenario": "AV:N - The vulnerable code is reached when nfsd decodes an attacker-supplied NFS file handle (exportfs_decode_fh \u2192 isofs_fh_to_dentry), so a remote NFS client triggers it over the network (TCP/UDP 2049).\nAC:L - The attacker fully controls the block field in the file handle and the read is deterministic; no race or uncontrollable memory layout is involved.\nPR:N - The decode runs before per-user permission checks, and the realistic deployment (a read-only ISO exported to a subnet via default AUTH_SYS) lets any permitted network peer craft handles without credentials.\nUI:N - The NFS server processes the crafted request automatically; no victim action is required at attack time beyond the pre-existing export.\nS:U - The impact stays within the kernel filesystem/NFS security authority; no cross-authority boundary (VM, IOMMU, sandbox) is crossed.\nC:H - An out-of-bounds (cross-partition) read of arbitrary in-range blocks on the backing device is disclosed to the NFS client as inode metadata, and is not bounded to a few bytes since the attacker can probe blocks across the device.\nI:N - isofs is mounted strictly read-only and the commit confirms no memory-safety violation, so the attacker cannot modify any data or kernel memory.\nA:N - Out-of-range reads return NULL cleanly via the EIO path and in-range parsing is bounded; the commit and maintainer explicitly confirm no crash, hang, or memory-safety fault."
    }
  }
}