TI-2026-05988 Aliases CVE-2026-6827 GHSA-f8m6-5gph-fw7f

justhtml before 1.17.0 Multiple Cross-Site Scripting Vulnerabilities

LOW 23CWE-79Published 2026-08-23 · Updated 2026-08-29

Key facts

Attack vector: Network
Privileges required: None
User interaction: Active
Attack complexity: Low
Attack requirements: None
Impact type: Cross-site scripting
Confidentiality · integrity · availability: None · None · None
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-79.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00261 17th percentileScored 2026-11-07

Fix Fixed justhtml (EmilStenstrom): 1.17.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
EmilStenstrom	justhtml	before 1.17.0	1.17.0	Patch available	CNA

justhtml VendorEmilStenstrom Affected before 1.17.0 Fixed in 1.17.0 Patch available CNA

Remediation

Fix · CNA justhtml (EmilStenstrom) Fixed in 1.17.0

Timeline

2026-10-02 Threatist record created from CVE-2026-6827
2026-10-03 Alias added: GHSA-f8m6-5gph-fw7f

References

Advisory 1

GitHub Security Advisory (GHSA-vrx2-77f2-ww34)

TI-2026-07422 justhtml before 1.12.0 Sanitizer Bypass via Markdown CVSS 4.0CRITICAL 9.3
TI-2026-08560 justhtml before 1.10.0 Denial of Service via deeply nested HTML CVSS 4.0HIGH 8.7
TI-2026-52557 justhtml before 3.11.0 XSS via selectedcontent projection CVSS 4.0MEDIUM 5.1
TI-2026-04717 justhtml before 1.13.0 XSS via code fence breakout CVSS 4.0MEDIUM 5.1
TI-2026-06871 justhtml before 1.16.0 Multiple Security Issues via Sanitization CVSS 4.0CRITICAL 9.3
TI-2026-04716 justhtml before 1.15.0 Multiple Security Issues CVSS 4.0CRITICAL 9.3

See all 10 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences