CVE-2026-56317: Nuxt Cross-Site Scripting Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-m3q2-p4fw-w38m",
  "modified" : "2026-09-09T23:50:59Z",
  "published" : "2026-06-16T23:38:47Z",
  "aliases" : [ "CVE-2026-56317" ],
  "summary" : "Cross-site scripting via <NoScript> slot content in Nuxt's head components",
  "details" : "### Impact\n\nNuxt's globally registered `<NoScript>` component (from `@unhead/vue` head components, re-exported by Nuxt) wrote its default-slot content to the `innerHTML` of the `<noscript>` head tag, bypassing the HTML escaping that `{{ }}` interpolation normally applies in Vue templates.\n\nApplications that placed untrusted, attacker-controllable data inside a `<NoScript>` slot, for example:\n\n```vue\n<NoScript>{{ route.query.banner }}</NoScript>\n```\n\nwould emit that value unescaped inside `<noscript>` in the server-rendered HTML. With scripting enabled, the HTML parser treats `<noscript>` content in `<head>` under the \"in head noscript\" insertion mode: any tag other than `link`, `meta`, `noframes`, or `style` implicitly closes `<noscript>` and is re-processed in the head. A payload such as `<script>...</script>` therefore escapes the element and executes in the document context.\n\nSibling head components (`<Style>`, `<Title>`) were not affected because they already routed slot text through the safe `textContent` path.\n\n### Affected versions\n\nAll currently supported versions of `nuxt` that ship the `<NoScript>` global component.\n\n### Patches\n\nFixed in `nuxt@4.4.7` (commit [`4b054e9d`](https://github.com/nuxt/nuxt/commit/4b054e9d95f8daf366cb144b52782047c511a66e)) and backported to `nuxt@3.21.7` (commit [`7fea9fd6`](https://github.com/nuxt/nuxt/commit/7fea9fd687f1dacbfb63db5fae5839896b017a0e)). The fix escapes `<NoScript>` slot content with `escapeHtml` from `@vue/shared` and writes it to `textContent` rather than `innerHTML`. Slot content is now rendered as text; intentional markup inside `<NoScript>` is no longer parsed as HTML.\n\n### Workarounds\n\nUntil you can upgrade:\n\n- Do not interpolate untrusted input into `<NoScript>` slots. Replace `<NoScript>{{ x }}</NoScript>` with a static string, or sanitise / HTML-escape `x` at the source.\n- If you must render dynamic noscript content, write the tag yourself via `useHead({ noscript: [{ textContent: escapedValue }] })` after escaping `escapedValue`.\n\n### Credit\n\nReported to Anthropic's coordinated vulnerability disclosure pipeline by Claude (Anthropic's AI assistant) and triaged by the Anthropic security team. Reference: ANT-2026-4NJYDFFM.\n\nIndependently reported by [@alcls01111](https://github.com/alcls01111) via GitHub's coordinated disclosure flow (`GHSA-8grp-wcq9-925q`), closed as a duplicate of this advisory.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "nuxt"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.4.7"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "nuxt"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.21.7"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/nuxt/nuxt/security/advisories/GHSA-m3q2-p4fw-w38m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-56317"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nuxt/nuxt/commit/4b054e9d95f8daf366cb144b52782047c511a66e"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nuxt/nuxt/commit/7fea9fd687f1dacbfb63db5fae5839896b017a0e"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nuxt/nuxt"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/nuxt-cross-site-scripting-via-noscript-component-slot-content"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-16T23:38:47Z",
    "nvd_published_at" : null
  }
}