EUVD-2026-20992
GHSA-95h2-gj7x-gx9w
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Lifecycle Timeline
4Description
Unhead is a document head and template manager. Prior to 2.1.13, useHeadSafe() is the composable that Nuxt's own documentation explicitly recommends for rendering user-supplied content in <head> safely. Internally, the hasDangerousProtocol() function in packages/unhead/src/plugins/safe.ts decodes HTML entities before checking for blocked URI schemes (javascript:, data:, vbscript:). The decoder uses two regular expressions with fixed-width digit caps. The HTML5 specification imposes no limit on leading zeros in numeric character references. When a padded entity exceeds the regex digit cap, the decoder silently skips it. The undecoded string is then passed to startsWith('javascript:'), which does not match. makeTagSafe() writes the raw value directly into SSR HTML output. The browser's HTML parser decodes the padded entity natively and constructs the blocked URI. This vulnerability is fixed in 2.1.13.
Analysis
Unhead's useHeadSafe() composable, explicitly recommended by Nuxt documentation for safely rendering user-supplied content in document head, can be bypassed via padded HTML numeric character references that exceed regex digit limits. The hasDangerousProtocol() function silently fails to decode these entities, allowing blocked URI schemes (javascript:, data:, vbscript:) to pass validation; browsers then natively decode the padded entity during HTML parsing, enabling cross-site scripting (XSS) attacks. …
Sign in for full analysis, threat intelligence, and remediation guidance.
Priority Score
Share
External POC / Exploit Code
Leaving vuln.today