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CVE-2026-7808— justhtml before 1.16.0 Multiple Security Issues via Sanitization

Quick assessment

Affected
EmilStenstrom justhtml
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

EmilStenstrom JustHTML是EmilStenstrom个人开发者开源的一个纯 Python HTML5 解析器。 EmilStenstrom JustHTML 1.16.0之前版本存在输入验证错误漏洞，该漏洞源于多个HTML清理绕过问题，可能导致活动或危险内容绕过清理，造成跨站脚本攻击。

CVSS 9.8 · Critical EPSS 0.59% · P47

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-2026-7808

Vulnerability Information
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Vulnerability Title
justhtml before 1.16.0 Multiple Security Issues via Sanitization
Source: CVE Program / CVE List V5
Vulnerability Description
justhtml before 1.16.0 contains multiple HTML sanitization bypass issues that can allow active/dangerous content (e.g., script or style) to survive sanitization, potentially leading to cross-site scripting. The issues primarily affect advanced usage rather than the default JustHTML(..., sanitize=True) path for ordinary parsed HTML: mutating or reusing sanitization policy objects (including exported defaults) could weaken later sanitization; programmatic DOM input to sanitize()/sanitize_dom() could miss mixed-case tag names (e.g., ScRiPt, StYlE); crafted programmatic doctype names could serialize into active markup; and custom policies preserving SVG or MathML could allow animation elements, presentation attributes with external url(...) references, or DOM trees mislabeled as namespace="html" to bypass foreign-content checks. Fixed in 1.16.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
EmilStenstrom JustHTML 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
EmilStenstrom JustHTML是EmilStenstrom个人开发者开源的一个纯 Python HTML5 解析器。 EmilStenstrom JustHTML 1.16.0之前版本存在输入验证错误漏洞，该漏洞源于多个HTML清理绕过问题，可能导致活动或危险内容绕过清理，造成跨站脚本攻击。
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
EmilStenstrom justhtml 0 ~ 1.16.0 -

II. Public POCs for CVE-2026-7808

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 10288 chars
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Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
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Exploit chain & mitigation
POC zip download
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III. Intelligence Information for CVE-2026-7808

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Vendor Advisories for CVE-2026-7808 (2)

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

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-2026-6827 6.1 MEDIUM justhtml before 1.17.0 Multiple Cross-Site Scripting Vulnerabilities
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-20