{
  "cveId": "CVE-2026-31712",
  "url": "https://patchblox.com/security/cve/CVE-2026-31712",
  "summary": "CVE-2026-31712 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-31712, released May 15, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "ksmbd: require minimum ACE size in smb_check_perm_dacl()",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  ksmbd: require minimum ACE size in smb_check_perm_dacl()  Both ACE-walk loops in smb_check_perm_dacl() only guard against an under-sized remaining buffer, not against an ACE whose declared \u0060ace-\u003Esize\u0060 is smaller than the struct it claims to describe:    if (offsetof(struct smb_ace, access_req) \u003E aces_size)       break;   ace_size = le16_to_cpu(ace-\u003Esize);   if (ace_size \u003E aces_size)       break;  The first check only requires the 4-byte ACE header to be in bounds; it does not require access_req (4 bytes at offset 4) to be readable. An attacker who has set a crafted DACL on a file they own can declare ace-\u003Esize == 4 with aces_size == 4, pass both checks, and then    granted |= le32_to_cpu(ace-\u003Eaccess_req);               /* upper loop */   compare_sids(\u0026sid, \u0026ace-\u003Esid);                         /* lower loop */  reads access_req at offset 4 (OOB by up to 4 bytes) and ace-\u003Esid at offset 8 (OOB by up to CIFS_SID_BASE_SIZE \u002B SID_MAX_SUB_AUTHORITIES * 4 bytes).  Tighten both loops to require    ace_size \u003E= offsetof(struct smb_ace, sid) \u002B CIFS_SID_BASE_SIZE  which is the smallest valid on-wire ACE layout (4-byte header \u002B 4-byte access_req \u002B 8-byte sid base with zero sub-auths).  Also reject ACEs whose sid.num_subauth exceeds SID_MAX_SUB_AUTHORITIES before letting compare_sids() dereference sub_auth[] entries.  parse_sec_desc() already enforces an equivalent check (lines 441-448); smb_check_perm_dacl() simply grew weaker validation over time.  Reachability: authenticated SMB client with permission to set an ACL on a file.  On a subsequent CREATE against that file, the kernel walks the stored DACL via smb_check_perm_dacl() and triggers the OOB read.  Not pre-auth, and the OOB read is not reflected to the attacker, but KASAN reports and kernel state corruption are possible.",
  "published": "2026-05-01T14:16:21Z",
  "severity": "Important",
  "cvss": 8.3,
  "cvssVector": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H",
  "epss": 0.00323,
  "epssPercentile": 0.2548,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-31712",
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 12.15 (bookworm)",
      "fixedVersion": "6.1.176-1",
      "fix": "DEBIAN-CVE-2026-31712",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-31712",
      "released": "2026-05-15T16:01:09Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.12.85-1",
      "fix": "DEBIAN-CVE-2026-31712",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-31712",
      "released": "2026-05-15T16:01:09Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.0.3-1",
      "fix": "DEBIAN-CVE-2026-31712",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-31712",
      "released": "2026-05-15T16:01:09Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-09T01:18:40Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}