XSS in Unjs Unhead
CVE-2026-31860
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.
Vulnerability class: XSS (Cross-Site Scripting)
EPSS: 0.003 (17.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
Affected products
- Unjs Unhead — versions < 2.1.11
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-31860?
- CVE-2026-31860 is a medium-severity vulnerability in Unjs Unhead, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-03-12.
- How severe is CVE-2026-31860?
- Medium severity. CVSS v3 base score is 6.1 out of 10.