{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "sanitize-html"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.18.0"
            },
            {
              "fixed": "2.18.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-113650"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-21T17:05:01Z",
    "nvd_published_at": "2026-10-20T17:17:35Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nSince 2.18.0, when an `\u003ciframe\u003e` is not allowed and `disallowedTagsMode` is `\u0027discard\u0027` (the defaults),\nits raw-text content is re-sanitized by a recursive call to `sanitizeHtml(text, options)` (the change\nfrom #5564, fixing #5550). The recursion has no bound and starts each nested call with a fresh state.\nTwo consequences, both absent from 2.17.7 and 2.17.4:\n\n1. A few kilobytes of unclosed `\u003ciframe\u003e` tags throw `RangeError: Maximum call stack size exceeded`\n   with the default options. Any application that sanitizes untrusted HTML with 2.18.0 can be made to\n   throw on a small crafted input.\n2. `nestingLimit` is not enforced across a discarded iframe: each nested iframe restarts the depth\n   count at zero, so the output can be nested arbitrarily deep regardless of the configured limit.\n\n### Affected versions\n\n- 2.18.0 (the current `latest`), and the `main` branch at the time of writing (the recursive call is\n  still in `packages/sanitize-html/index.js`, in the `ontext` handler, branch\n  `tag === \u0027iframe\u0027 \u0026\u0026 !tagAllowed(tag) \u0026\u0026 options.disallowedTagsMode === \u0027discard\u0027`).\n- Not affected: 2.17.7 and 2.17.4 (tested with the same inputs below).\n\nTested with Node.js v26.7.0.\n\n### Reproduction 1: stack overflow with the default options\n\n```js\nconst sanitizeHtml = require(\u0027sanitize-html\u0027);\n\n// with 2.18.0:\nsanitizeHtml(\u0027\u003ciframe\u003e\u0027.repeat(1000));  // 8,000 chars: returns \u0027\u0027\nsanitizeHtml(\u0027\u003ciframe\u003e\u0027.repeat(2000));  // 16,000 chars: throws RangeError: Maximum call stack size exceeded\nsanitizeHtml(\u0027\u003ciframe\u003e\u0027.repeat(20000)); // 160,000 chars: throws RangeError: Maximum call stack size exceeded\n```\n\nResults:\n\n| input | 2.17.4 | 2.17.7 | 2.18.0 |\n|---|---|---|---|\n| `\u0027\u003ciframe\u003e\u0027.repeat(1000)` | ok | ok | ok |\n| `\u0027\u003ciframe\u003e\u0027.repeat(2000)` | ok | ok | RangeError |\n| `\u0027\u003ciframe\u003e\u0027.repeat(20000)` | ok | ok | RangeError |\n\nThe threshold depends on the remaining stack, so it is lower when `sanitizeHtml` is called from an\nalready deep call stack (for example inside a server-side rendering pass).\n\n### Reproduction 2: `nestingLimit` is bypassed\n\n```js\nconst sanitizeHtml = require(\u0027sanitize-html\u0027);\n\nconst input = (\u0027\u003ciframe\u003e\u0027 + \u0027\u003cb\u003e\u0027.repeat(3)).repeat(50) + \u0027x\u0027;\nconst out = sanitizeHtml(input, { allowedTags: [\u0027b\u0027], nestingLimit: 3 });\n// maximum nesting depth of \u003cb\u003e in `out`:\n//   2.17.4: 2    2.17.7: 0 (fallback escaped as text)    2.18.0: 150\n```\n\nWithout an iframe, the same options cap the output at three nested `\u003cb\u003e` in all three versions. With\n`k` repetitions of `\u0027\u003ciframe\u003e\u0027 + \u0027\u003cb\u003e\u0027.repeat(3)`, 2.18.0 returns `3 * k` nested `\u003cb\u003e` (measured for\nk = 1, 5, 50: depth 3, 15, 150).\n\n### Cause\n\nIn 2.18.0 the `ontext` handler does:\n\n```js\n} else if (\n  tag === \u0027iframe\u0027 \u0026\u0026\n  !tagAllowed(tag) \u0026\u0026\n  options.disallowedTagsMode === \u0027discard\u0027\n) {\n  result += sanitizeHtml(text, options);\n}\n```\n\nBecause htmlparser2 treats `\u003ciframe\u003e` as a raw-text element, the text of an unclosed iframe is the whole\nremainder of the input; re-parsing it can meet another unclosed `\u003ciframe\u003e`, and so on, one stack frame\n(and one full re-parse) per iframe. The nested call also starts with its own `depth`, so tags inside the\nfallback are not counted against `nestingLimit` together with the enclosing tags.\n\n### Possible directions\n\nNot a patch, only what would close both effects: bound the recursion (or process the fallback without\nrecursing), and carry the current depth into the nested sanitization so that `nestingLimit` applies to\nthe whole output.",
  "id": "GHSA-c9rx-x947-fp3h",
  "modified": "2026-10-21T17:05:01Z",
  "published": "2026-10-21T17:05:01Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-c9rx-x947-fp3h"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-113650"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/commit/06e4b377f3c360f9e89c32dccd7e505ad5ddf498"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/commit/40b989b1a9dd23d30029b8ce7668634265cfe5ea"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/apostrophecms/apostrophe"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apostrophecms/apostrophe/releases/tag/sanitize-html@2.18.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "ApostropheCMS sanitize-html: unbounded recursion when re-sanitizing the fallback of a discarded iframe (stack overflow, nestingLimit not enforced)"
}