CVE-2026-84374: Maatwebsite/excel Laravel Excel Writes Exports Outside Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-c7r6-vx3h-w5g2",
  "modified" : "2026-09-08T20:40:47Z",
  "published" : "2026-09-08T20:40:47Z",
  "aliases" : [ "CVE-2026-84374" ],
  "summary" : "Laravel Excel writes exports outside the configured filesystem disk when given a caller-controlled path",
  "details" : "### Summary\n\n`Excel::store()` resolved the destination path against the process working\ndirectory rather than the configured filesystem disk. When that path resolved to\nan existing file, the export was written straight to it with `fopen()`,\nbypassing the disk entirely. An application that passes a user-controlled value\nas the export path could therefore be made to overwrite an arbitrary existing\nfile that the PHP process can write to, with content the user controls.\n\n### Details\n\n`Maatwebsite\\Excel\\Files\\Disk::copy()` contained two paths:\n\n```php\nif (realpath($destination)) {\n    $tempStream = fopen($destination, 'rb+');\n    $success    = stream_copy_to_stream($readStream, $tempStream) !== false;\n} else {\n    $success = $this->put($destination, $readStream);\n}\n```\n\n`$destination` is the `$filePath` argument given to `Excel::store()`,\n`$export->store()` or `->storeExcel()`. `realpath()` resolves it against the\n**current working directory** — `public/` for a typical web request — not\nagainst the disk root. On a hit, the write went directly to the filesystem and\nnever reached Flysystem, which would otherwise have rejected `../` traversal and\nconfined absolute paths to the disk root. The disk argument was effectively\nignored for those paths, including for remote disks such as S3.\n\nTwo consequences follow:\n\n* the destination could be any existing file the PHP process can write, in or\n  out of the disk root;\n* the stream was opened `'rb+'`, which does not truncate, so a shorter export\n  left trailing bytes of the previous file behind.\n\nBecause the file must already exist, the primitive is an **overwrite** rather\nthan an arbitrary file creation. Overwriting a PHP file that is reachable by the\nweb server (for example a front controller or a cached view) turns\nattacker-controlled row content into code execution, since CSV and HTML writers\nemit cell values verbatim. Passing an explicit writer type to `store()` bypasses\nthe extension-based type detection that would otherwise reject a `.php` target.\n\nExploitation requires the **application** to pass an unsanitized, user-controlled\nvalue as the export path. Applications that pass a fixed or server-derived path\nare not affected.\n\n### Impact\n\nArbitrary overwrite of existing files writable by the PHP process, with\npartially attacker-controlled content, leading to remote code execution where\nthe overwritten file is executed by the web server.\n\n### Patches\n\nFixed in **3.1.70**. `Disk::copy()` now always writes through the configured\nfilesystem disk, so Flysystem enforces the disk root for every export.\n\nNote the behaviour change: passing an absolute path to `store()` previously\nwrote to that path once the file existed. Paths now always resolve relative to\nthe disk root. Applications that relied on that should configure a disk rooted\nat the target location.\n\n### Workarounds\n\nFor anyone unable to upgrade, validate the path before passing it to `store()` —\nreject absolute paths and any `..` segment, or derive the filename server-side\nand never build it from request input:\n\n```php\n$name = basename($request->input('filename'));   // strips any directory part\nExcel::store($export, 'exports/' . $name, 'local');\n```\n\n### Credit\n\nReported responsibly by @seck19 via the contact address in `SECURITY.md`.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "maatwebsite/excel"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.1.8"
      }, {
        "fixed" : "3.1.70"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/SpartnerNL/Laravel-Excel/security/advisories/GHSA-c7r6-vx3h-w5g2"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-84374"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/SpartnerNL/Laravel-Excel/commit/b5cafdfcf7ec63924e83303763be8fcae340f70b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/SpartnerNL/Laravel-Excel"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/SpartnerNL/Laravel-Excel/releases/tag/3.1.70"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22", "CWE-73" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-08T20:40:47Z",
    "nvd_published_at" : "2026-09-01T22:17:19Z"
  }
}