{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "cc20c031bb067eb3280a1c4b5c42295093e24863"
            },
            {
              "fixed": "3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2d"
            },
            {
              "fixed": "411e484fe71a7f1028de617447edad9cb6d9d68a"
            },
            {
              "fixed": "65deb18359341141d37dc86fc7853511be3c87a7"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.6.30"
            },
            {
              "fixed": "6.18.51"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.2.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89631.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: reject a tree connect response whose byte count is too small\n\nCIFSTCon() bounds its strnlen() over the byte area with the server's\nByteCount minus two, which for ByteCount 0 or 1 goes negative as an int\nand converts to a huge size_t.  The later subtraction wraps the __u16\nbytes_left, and that is what bounds cifs_strndup_from_utf16(): a bound of\nup to 65535 against a ~16 KB cifs_req_poolp object runs off the end of the\nslab object, and the bytes reach userspace through tcon-\u003enativeFileSystem\nin /proc/fs/cifs/DebugData.\n\nReject a byte area too small for what the parser consumes.  Two bytes is\nthe least it can consume, and no conformant response carries fewer.  The\nnew trace point is the 129th smb_eio_trace entry, which __mode(byte)\ncannot represent, so the attribute goes with it.",
  "id": "CVE-2026-89631",
  "modified": "2026-09-15T03:30:37.835898845Z",
  "published": "2026-09-11T19:45:26.444Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/411e484fe71a7f1028de617447edad9cb6d9d68a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/65deb18359341141d37dc86fc7853511be3c87a7"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89631.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89631"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "smb: client: reject a tree connect response whose byte count is too small"
}