CVE-2026-39315

The record

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.

Affected packages

Related vulnerabilities

• GHSA-95h2-gj7x-gx9w Unhead has a hasDangerousProtocol() bypass via leading-zero padded HTML entities in… Same vulnerability
• GHSA-x7mm-9vvv-64w8 unhead: Streaming SSR `streamKey` injected into inline script without identifier… Also affects unhead
• CVE-2026-31873 Unhead is a document head and template manager. Also affects unhead
• CVE-2026-31860 Unhead is a document head and template manager. Also affects unhead
• GHSA-5339-hvwr-7582 Unhead Vulnerable to Bypass of URI Scheme Sanitization in makeTagSafe via Case-Sensitivity Also affects unhead
• GHSA-g5xx-pwrp-g3fv Unhead has XSS bypass in `useHeadSafe` via attribute name injection and case-sensitive… Also affects unhead
• CVE-2026-114729 Roundcube Webmail before 1.6.20 and 1.7.x before 1.7.5 is affected by a remote content… CWE-184
• CVE-2026-114728 Roundcube Webmail before 1.6.20 and 1.7.x before 1.7.5 is affected by a remote content… CWE-184