CVE-2026-31873noneCWE-79

CVE-2026-31873: vulnerability in unjs unhead

Unhead has a Bypass of URI Scheme Sanitization in makeTagSafe via Case-Sensitivity

Published

Follow this CVE+ Monitor unhead+ Monitor unhead

E-mail alert when it lands in KEV, gets a public PoC or its score goes up.

3Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 0epss 0.2%
Unhead is a document head and template manager. Prior to 2.1.11, The link.href check in makeTagSafe (safe.ts) uses String.includes(), which is case-sensitive. Browsers treat URI schemes case-insensitively. DATA:text/css,... is the same as data:text/css,... to the browser, but 'DATA:...'.includes('data:') returns false. An attacker can inject arbitrary CSS for UI redressing or data exfiltration via CSS attribute selectors with background-image callbacks. This vulnerability is fixed in 2.1.11.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N
Affected products
unjs · unhead
Related CVEs — unjs unhead

In the same product, most dangerous first.

CVE-2026-39315MEDIUMUnhead has a hasDangerousProtocol() bypass via leading-zero padded HTML entities in useHeadSafe()EPSS 0.3%CVE-2026-31860MEDIUMUnhead has a XSS bypass in `useHeadSafe` via attribute name injection and case-sensitive protocol checkEPSS 0.3%