CVE-2026-31873
Unhead has a Bypass of URI Scheme Sanitization in makeTagSafe via Case-Sensitivity
CVSS Score
0.0
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-79 |
| Vendor | unjs |
| Product | unhead |
| Published | Mar 12, 2026 |
| Last Updated | Mar 12, 2026 |
Stay Ahead of the Next One
Get instant alerts for unjs unhead
Be the first to know when new unknown vulnerabilities affecting unjs unhead are published — delivered to Slack, Telegram or Discord.
Get Free Alerts →
Free · No credit card · 60 sec setup
CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
None
Affected Versions
unjs / unhead
< 2.1.11