{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:12",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.1.176-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:13",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.12.85-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.0.3-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "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 `ace-\u003esize` 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 + SID_MAX_SUB_AUTHORITIES * 4 bytes).  Tighten both loops to require    ace_size \u003e= offsetof(struct smb_ace, sid) + CIFS_SID_BASE_SIZE  which is the smallest valid on-wire ACE layout (4-byte header + 4-byte access_req + 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.",
  "id": "DEBIAN-CVE-2026-31712",
  "modified": "2026-09-14T16:47:36.796482870Z",
  "published": "2026-05-01T14:16:21.270Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-31712"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H",
      "type": "CVSS_V3"
    }
  ],
  "upstream": [
    "CVE-2026-31712"
  ]
}