CVE-2026-31860
CVE-2026-31860 is a Cross-site Scripting (XSS) vulnerability in unhead. O3 Security confirms whether CVE-2026-31860 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Unhead has a XSS bypass in `useHeadSafe` via attribute name injection and case-sensitive protocol check
Real-World Exposure
unheadReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | unhead | all versions | 2.1.11 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for unhead. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update unhead to 2.1.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-31860 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-31860 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-31860. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-31860 in your dependencies?
O3 detects CVE-2026-31860 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.