CVE-2026-31873

NONE

unjs/unhead < 2.1.11 - Cross-Site Scripting via Case-Insensitive URI Scheme Bypass

Title source: llm
STIX 2.1

Description

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.

References (1)

Core 1
Core References

Scores

CVSS v3 0.0
EPSS 0.0024
EPSS Percentile 14.5%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N

CISA SSVC

Vulnrichment
Exploitation poc
Automatable yes
Technical Impact partial

Details

CWE
CWE-79
Status published
Products (1)
unjs/unhead < 2.1.11
Published Mar 12, 2026
Tracked Since Mar 13, 2026