CVE-2026-33418: @dicebear/converter SVG Dimension Capping Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-7j2x-32w6-p43p",
  "modified" : "2026-03-25T20:53:40Z",
  "published" : "2026-03-20T20:35:40Z",
  "aliases" : [ "CVE-2026-33418" ],
  "summary" : "SVG Dimension Capping Bypass via XML Comment Injection in @dicebear/converter ensureSize()",
  "details" : "## Summary\n\nThe `ensureSize()` function in `@dicebear/converter` used a regex-based approach to rewrite SVG `width`/`height` attributes, capping them at 2048px to prevent denial of service. This size capping could be bypassed by crafting SVG input that causes the regex to match a non-functional occurrence of `<svg` before the actual SVG root element. When the SVG is subsequently rendered via `@resvg/resvg-js` on the Node.js code path, it renders at the attacker-specified dimensions, potentially causing out-of-memory crashes.\n\n## Details\n\nThe vulnerable function used `String.prototype.replace()` with a non-global regex to find and rewrite the first `<svg` tag's dimensions. Since the regex does not distinguish between `<svg` appearing inside non-element XML constructs and the actual SVG root element, a crafted input can cause the regex to match a decoy instead of the real element, leaving the actual SVG dimensions unclamped.\n\nIn the Node.js rendering path, `renderAsync` from `@resvg/resvg-js` was called without a `fitTo` constraint, so it would render at whatever dimensions the SVG element specified — potentially allocating gigabytes of memory.\n\nThe browser code path is **not** vulnerable because it uses the clamped `size` return value from `ensureSize()` to set `canvas.width` and `canvas.height` directly.\n\n## Impact\n\nAny application that passes untrusted or user-supplied SVG content through `@dicebear/converter`'s Node.js conversion functions (`toPng`, `toJpeg`, `toWebp`, `toAvif`) is vulnerable to denial of service via excessive memory allocation. Note that `@dicebear/converter` can be used independently of DiceBear's avatar generation — any SVG string can be passed to the conversion functions.\n\nThe impact is limited to availability — there is no data disclosure or integrity impact. The browser code path is not affected.\n\n## Fix\n\nThe regex-based approach has been replaced with XML-aware processing using `fast-xml-parser` to correctly identify and modify the SVG root element's attributes. Additionally, a `fitTo` constraint has been added to the `renderAsync` call as defense-in-depth, ensuring the rendered output is always bounded regardless of SVG content.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@dicebear/converter"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "9.4.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 9.4.1"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/dicebear/dicebear/security/advisories/GHSA-7j2x-32w6-p43p"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33418"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/dicebear/dicebear"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-185" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-20T20:35:40Z",
    "nvd_published_at" : "2026-03-24T14:16:30Z"
  }
}