CVE-2026-31873 NONE

CVE-2026-31873: Unhead has a Bypass of URI Scheme Sanitization in makeTagSafe via Case-Sensitivity

Vendor Unjs
Product unhead
Weakness CWE-79 · XSS
Published March 12, 2026
Last update March 12, 2026
View on NVD All CVEs

CVSS base score

0.0/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality None
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

March 12, 2026 CVE published
March 12, 2026 Record updated