CVE-2026-31860 Unhead has a XSS bypass in `useHeadSafe` via attribute name injection and case-sensitive protocol check
Attackers can bypass XSS protections in Unhead to inject malicious HTML attributes into server-side rendered pages, potentially executing arbitrary scripts.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-31860?
CVE-2026-31860 is a medium-severity cross-site scripting vulnerability in unjs unhead, published on 12 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-31860?
2 open source packages ship an affected version, including unhead. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
unhead npm | All versions | 2.1.11 |
unhead npm | All versions | 2.1.11 |
Products include Unjs Unhead.
How do I fix CVE-2026-31860?
Upgrade unhead to 2.1.11 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-31860 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-31860 exists.
Other vulnerabilities in unjs unhead
Sources
Also known as GHSA-g5xx-pwrp-g3fv.