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

Quick assessment

Affected
unjs unhead
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

unhead是UnJS开源的一个文档头和模板管理器。 unhead 2.1.11之前版本存在跨站脚本漏洞，该漏洞源于link.href检查对大小写敏感，可能导致攻击者注入任意CSS，用于UI伪装或通过CSS属性选择器进行数据渗漏。

EPSS 0.27% · P17
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I. Basic Information for CVE-2026-31873

Vulnerability Information
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Vulnerability Title
Unhead has a Bypass of URI Scheme Sanitization in makeTagSafe via Case-Sensitivity
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
unhead 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
unhead是UnJS开源的一个文档头和模板管理器。 unhead 2.1.11之前版本存在跨站脚本漏洞，该漏洞源于link.href检查对大小写敏感，可能导致攻击者注入任意CSS，用于UI伪装或通过CSS属性选择器进行数据渗漏。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
unjs unhead < 2.1.11 -

II. Public POCs for CVE-2026-31873

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III. Intelligence Information for CVE-2026-31873

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Vendor Advisories for CVE-2026-31873 (1)

IV. Related Vulnerabilities

Same product: unhead
Same vendor: unjs
Same weakness: CWE-79

V. Comments for CVE-2026-31873

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