CVE-2026-31873CWE-79

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

published March 12, 2026

CVSS v3.1
0.0
EPSS
0%
Percentile
17.8
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
0.0 · NONE
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00267 · 17.8th percentile
Weakness
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-03-12T17:20Z
EPSS history
Timeline
  • 12 MAR 17:20Z
    Unhead has a Bypass of URI Scheme Sanitization in makeTagSafe via Case-Sensitivity
    cvelistv5