---
id: CVE-2026-7808
title: >-
  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
summary: >-
  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 ad…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-20
vendor: justhtml
product: justhtml
affected:
  - justhtml < 1.16.0
patched:
  - justhtml 1.16.0
published: '2026-08-23'
updated: '2026-10-12'
sourceUpdated: '2026-10-12T16:10:00.220'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-7808'
references:
  - url: >-
      https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-4p64-v8f5-r2gx
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/justhtml-before-multiple-security-issues-via-sanitization
    label: disclosure@vulncheck.com
  - url: 'https://github.com/EmilStenstrom/justhtml'
tags:
  - nvd
  - osv
  - pip
epss: 0.00587
epssPercentile: 0.47875
aliases:
  - GHSA-4p64-v8f5-r2gx
ecosystem: pip
ingestedAt: '2026-08-24T19:25:44.052Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-7808)

Affected packages:

- `justhtml < 1.16.0`

Patched in:

- `justhtml 1.16.0`

Source: https://osv.dev/vulnerability/GHSA-4p64-v8f5-r2gx