{"id":"CVE-2026-114133","aliases":["GHSA-xfq5-w38q-pc2x"],"url":"https://o3.security/vulnerability/CVE-2026-114133","summary":"Nuxt server islands render `useHeadSafe` input without sanitisation","details":"## Impact\n\n`useHeadSafe` restricts head input to an allowlist of safe tags and attributes. For example, `bodyAttrs` is limited to `class` and `style`, event handler attributes are removed, and `<script>` tags are only kept for JSON types.\n\nWhen `useHeadSafe` is called inside a server island (a `.server.vue` component or page, or a component rendered with `<NuxtIsland>`), the island renderer serialises the raw input of every head entry into the island response without the option that marks it as safe input. `<NuxtIsland>` then pushes that input into the page's head as a regular entry, both during server rendering and when hydrating or refetching on the client.\n\nAs a result, input that `useHeadSafe` would normally strip (such as `bodyAttrs.onload` or executable `<script>` content) is rendered into the page. If an application passes user-controlled data to `useHeadSafe` inside a server island, an attacker who controls that data can achieve stored cross-site scripting on the application's origin.\n\n```vue\n<!-- components/AuthorMeta.server.vue -->\n<script setup lang=\"ts\">\nconst { data: author } = await useFetch('/api/author')\n// author.value.head is user-authored, e.g. { bodyAttrs: { onload: '...' } }\nuseHeadSafe(author.value.head)\n</script>\n```\n\n## Mitigating factors\n\n- Server components are experimental. They are only active when the application defines a `.server.vue` component or page, or enables `experimental.componentIslands` and renders `<NuxtIsland>`.\n- Exploitation requires the application to pass attacker-controlled data to `useHeadSafe` inside a server island. `useHeadSafe` called from regular (non-island) components and pages is not affected.\n\n## Affected versions\n\n`nuxt` `>=3.13.0`, when head support for server islands was introduced. Nuxt 2 is not affected.\n\n## Patches\n\nFixed in `nuxt@4.6.2`. Nuxt 3 reached end of life on 31 July 2026 and will not receive a fix.\n\nPatched releases apply Unhead's safe input filtering to `useHeadSafe` entries on the server before they are added to the island response, so `islandResponse.head` (including what `render:island` hooks see) only contains input that `useHeadSafe` allows.\n\n## Workarounds\n\nUpgrade to `nuxt@4.6.2`. If you cannot upgrade, including on Nuxt 3:\n\n1. Call `useHeadSafe` with untrusted input from a regular component or page rather than from inside a server island.\n2. Alternatively, validate untrusted head input against your own allowlist before passing it to `useHeadSafe` inside a server island.","published":"2026-10-21T17:52:09.381Z","modified":"2026-10-22T02:49:12.848992918Z","cvss":{"score":5.4,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"npm","name":"nuxt","fixedVersion":"4.6.2"}],"fix":{"url":"https://github.com/nuxt/nuxt/commit/493565e99451a0f52330b1f6b979254a4a39e5d0","label":"nuxt/nuxt@493565e"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/114xxx/CVE-2026-114133.json"},{"type":"FIX","url":"https://github.com/nuxt/nuxt/commit/493565e99451a0f52330b1f6b979254a4a39e5d0"},{"type":"WEB","url":"https://github.com/nuxt/nuxt/releases/tag/v4.6.2"},{"type":"ADVISORY","url":"https://github.com/nuxt/nuxt/security/advisories/GHSA-xfq5-w38q-pc2x"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-114133"},{"type":"PACKAGE","url":"https://github.com/nuxt/nuxt"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-22T02:49:12.848992918Z"}}