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GHSA-J2PV-CPRG-P57X

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:

nfsd: gate nfs3 setacl by argp->mask

nfsd3_proc_setacl() calls set_posix_acl() unconditionally for both ACL_TYPE_ACCESS and ACL_TYPE_DEFAULT, passing argp->acl_access and argp->acl_default verbatim. The NFSv3 ACL decoder only populates those pointers when the corresponding mask bit is set:

nfs3svc_decode_setaclargs()
  if (args->mask & NFS_ACL)    decode into acl_access
  if (args->mask & NFS_DFACL)  decode into acl_default
  /* otherwise the pointer stays NULL (pc_argzero) */

nfsd3_proc_setacl()
  set_posix_acl(.., ACL_TYPE_ACCESS,  argp->acl_access)
  set_posix_acl(.., ACL_TYPE_DEFAULT, argp->acl_default)

set_posix_acl(idmap, dentry, type, NULL) is the VFS "remove this ACL type" operation. A NULL pointer that means "the client did not send this arm" is therefore indistinguishable from "the client asked to remove this ACL". A SETACL with mask=NFS_ACL silently drops the directory's default ACL; mask=0 drops both.

The sibling nfsd3_proc_getacl() already consults argp->mask before touching each arm; mirror that in setacl.

Fix by wrapping each set_posix_acl() call in the matching mask bit check and initializing error to 0 before inode_lock so that a request with neither bit set leaves the on-disk ACLs untouched and returns nfs_ok. The out_drop_lock path and the unconditional posix_acl_release() at out: are preserved; both NULL-tolerate the skipped arms.

Severity
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
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{
  "affected": [],
  "aliases": [
    "CVE-2026-89671"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:19:53Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: gate nfs3 setacl by argp-\u003emask\n\nnfsd3_proc_setacl() calls set_posix_acl() unconditionally for both\nACL_TYPE_ACCESS and ACL_TYPE_DEFAULT, passing argp-\u003eacl_access and\nargp-\u003eacl_default verbatim. The NFSv3 ACL decoder only populates\nthose pointers when the corresponding mask bit is set:\n\n    nfs3svc_decode_setaclargs()\n      if (args-\u003emask \u0026 NFS_ACL)    decode into acl_access\n      if (args-\u003emask \u0026 NFS_DFACL)  decode into acl_default\n      /* otherwise the pointer stays NULL (pc_argzero) */\n\n    nfsd3_proc_setacl()\n      set_posix_acl(.., ACL_TYPE_ACCESS,  argp-\u003eacl_access)\n      set_posix_acl(.., ACL_TYPE_DEFAULT, argp-\u003eacl_default)\n\nset_posix_acl(idmap, dentry, type, NULL) is the VFS \"remove this\nACL type\" operation. A NULL pointer that means \"the client did not\nsend this arm\" is therefore indistinguishable from \"the client\nasked to remove this ACL\". A SETACL with mask=NFS_ACL silently\ndrops the directory\u0027s default ACL; mask=0 drops both.\n\nThe sibling nfsd3_proc_getacl() already consults argp-\u003emask before\ntouching each arm; mirror that in setacl.\n\nFix by wrapping each set_posix_acl() call in the matching mask bit\ncheck and initializing error to 0 before inode_lock so that a\nrequest with neither bit set leaves the on-disk ACLs untouched and\nreturns nfs_ok. The out_drop_lock path and the unconditional\nposix_acl_release() at out: are preserved; both NULL-tolerate the\nskipped arms.",
  "id": "GHSA-j2pv-cprg-p57x",
  "modified": "2026-09-14T15:32:33Z",
  "published": "2026-09-11T21:31:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89671"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3be1d8611dae4829e4608007db29f4a8748c37b2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/453d7198a0ab07a12d46e0575861ac7b932da17e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/68a80b26efdff1d09f8ae1773c6a915abb9e191d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b3bff820d068ea59767d4e91a3258231a879da5f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ff99ed007f065198fd723152405c22aa558f700b"
    }
  ],
  "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:N",
      "type": "CVSS_V3"
    }
  ]
}



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