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CVE-2026-6827— justhtml before 1.17.0 Multiple Cross-Site Scripting Vulnerabilities

Quick assessment

Affected
EmilStenstrom justhtml
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.

在 justhtml 1.17.0 版本之前，其在 sanitization（净化）、serialization（序列化）以及程序化 DOM 处理方面存在多个安全问题。当自定义策略允许保留外部命名空间（如 SVG 或 MathML）时，危险内容（例如 HTML 集成点：SVG 中的 、MathML 中的 ）以及利用解析器差异的 mutation-XSS（变异型跨站脚本）载荷可能绕过净化机制，并在重新解析后转换为可执行的 HTML 代码。此外，SVG 的 属性以及被保留的 标签仍可能导致资源加载型 CSS 攻击（如

CVSS 6.1 · Medium

Affected Version Matrix 2

VendorProduct Version RangeStatus
EmilStenstrom justhtml < 1.16.0 affected
1.16.0 unaffected
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I. Basic Information for CVE-2026-6827

Vulnerability Information
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Vulnerability Title
justhtml before 1.17.0 Multiple Cross-Site Scripting Vulnerabilities
Source: CVE Program / CVE List V5
Vulnerability Description
justhtml before 1.17.0 contains multiple security issues in sanitization, serialization, and programmatic DOM handling. When custom policies preserve foreign namespaces (SVG/MathML), dangerous content such as HTML integration points (SVG <foreignObject>, MathML <annotation-xml encoding="text/html">) and mutation-XSS parser-differential payloads could survive sanitization and become active HTML after reparse; SVG filter="url(...)" and preserved <style> could leave resource-loading CSS (@import, background-image:url()). Programmatic script/style/Comment nodes could serialize into active markup. Additional hardening fixes address sanitize-pipeline cache mutation and DOM parent/child cycles that could cause infinite loops. Most issues affect advanced or custom configurations rather than the default JustHTML(..., sanitize=True) safe path.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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

Affected Products

Vendor Product Affected Versions CPE Subscribe
EmilStenstrom justhtml 0 ~ 1.16.0 -

II. Public POCs for CVE-2026-6827

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III. Intelligence Information for CVE-2026-6827

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Vendor Advisories for CVE-2026-6827 (2)

Same Patch Batch · EmilStenstrom · 2026-08-23 · 11 CVEs total

CVE-2026-7808 9.8 CRITICAL justhtml before 1.16.0 Multiple Security Issues via Sanitization
CVE-2026-8445 9.8 CRITICAL justhtml before 1.12.0 Sanitizer Bypass via Markdown
CVE-2026-5388 9.8 CRITICAL justhtml before 1.15.0 Multiple Security Issues
CVE-2026-9769 7.5 HIGH justhtml before 1.10.0 Denial of Service via deeply nested HTML
CVE-2026-4671 7.5 HIGH justhtml before 1.18.0 Denial of Service via CSS Selector
CVE-2026-77088 6.1 MEDIUM justhtml 0.9.0 through 1.21.0 Cross-Site Scripting via code-span
CVE-2026-74793 6.1 MEDIUM justhtml before 3.11.0 XSS via selectedcontent projection
CVE-2026-8630 6.1 MEDIUM justhtml before 1.12.0 Mutation XSS via Raw Text Elements
CVE-2026-5751 6.1 MEDIUM justhtml before 1.14.0 Mutation XSS via custom sanitization policies
CVE-2026-5389 6.1 MEDIUM justhtml before 1.13.0 XSS via code fence breakout

IV. Related Vulnerabilities

Same product: justhtml
Same vendor: EmilStenstrom
Same weakness: CWE-79

V. Comments for CVE-2026-6827

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