CVE-2026-39315
Description
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
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
unheadnpm | < 2.1.13 | 2.1.13 |
Affected products
1Patches
11 file changed · +2 −2
packages/unhead/src/plugins/safe.ts+2 −2 modified@@ -16,8 +16,8 @@ const BlockedLinkRels = new Set(['canonical', 'modulepreload', 'prerender', 'pre const SafeAttrName = /^[a-z][a-z0-9\-]*[a-z0-9]$/i -const HtmlEntityHex = /&#x([0-9a-f]{1,6});?/gi -const HtmlEntityDec = /&#(\d{1,7});?/g +const HtmlEntityHex = /&#x([0-9a-f]+);?/gi +const HtmlEntityDec = /&#(\d+);?/g const HtmlEntityNamed = /&(tab|newline|colon|semi|lpar|rpar|sol|bsol|comma|period|excl|num|dollar|percnt|amp|apos|ast|plus|lt|gt|equals|quest|at|lsqb|rsqb|lcub|rcub|vert|hat|grave|tilde|nbsp);?/gi // eslint-disable-next-line no-control-regex const ControlChars = /[\x00-\x20]+/g
Vulnerability mechanics
Generated by null/stub on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
5- github.com/unjs/unhead/commit/961ea781e091853812ffe17f8cda17105d2d2299nvdPatchWEB
- github.com/unjs/unhead/security/advisories/GHSA-95h2-gj7x-gx9wnvdExploitMitigationVendor AdvisoryWEB
- github.com/advisories/GHSA-95h2-gj7x-gx9wghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-39315ghsaADVISORY
- github.com/unjs/unhead/releases/tag/v2.1.13nvdProductRelease NotesWEB
News mentions
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