Summary
Nuxt server islands render useHeadSafe input without sanitisation
Mitigating factors
- Server components are experimental. They are only active when the application defines a
.server.vuecomponent or page, or enablesexperimental.componentIslandsand renders<NuxtIsland>. - Exploitation requires the application to pass attacker-controlled data to
useHeadSafeinside a server island.useHeadSafecalled from regular (non-island) components and pages is not affected.
Affected versions
nuxt >=3.13.0, when head support for server islands was introduced. Nuxt 2 is not affected.
Workarounds
Upgrade to [email protected]. If you cannot upgrade, including on Nuxt 3:
- Call
useHeadSafewith untrusted input from a regular component or page rather than from inside a server island. - Alternatively, validate untrusted head input against your own allowlist before passing it to
useHeadSafeinside a server island.
Impact
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.
When 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.
As 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.
<!-- components/AuthorMeta.server.vue -->
<script setup lang="ts">
const { data: author } = await useFetch('/api/author')
// author.value.head is user-authored, e.g. { bodyAttrs: { onload: '...' } }
useHeadSafe(author.value.head)
</script>
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
CVE-2026-114133 has a CVSS score of 5.4 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.6.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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See it in your environmentNew to Kodem? Get a demo →Remediation advice
Fixed in [email protected]. Nuxt 3 reached end of life on 31 July 2026 and will not receive a fix.
Patched 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.
Frequently Asked Questions
- What is CVE-2026-114133? CVE-2026-114133 is a medium-severity cross-site scripting (XSS) vulnerability in nuxt (npm), affecting versions >= 3.13.0, < 4.6.2. It is fixed in 4.6.2. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- How severe is CVE-2026-114133? CVE-2026-114133 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of nuxt are affected by CVE-2026-114133? nuxt (npm) versions >= 3.13.0, < 4.6.2 is affected.
- Is there a fix for CVE-2026-114133? Yes. CVE-2026-114133 is fixed in 4.6.2. Upgrade to this version or later.
- Is CVE-2026-114133 exploitable, and should I be worried? Whether CVE-2026-114133 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-114133 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-114133? Upgrade
nuxtto 4.6.2 or later.