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TI-2026-04716 Aliases CVE-2026-5388GHSA-9ph2-9r4x-rhjp

justhtml before 1.15.0 Multiple Security Issues

Priority MEDIUM 49CWE-20Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
—
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA.

Summary

justhtml before 1.15.0 contains multiple security issues in URL sanitization helpers (clean_url_value/clean_url_in_js_string), HTML serialization, Markdown passthrough (html_passthrough=True), and several custom sanitization-policy edge cases. Depending on configuration, an attacker can bypass sanitization to inject active HTML and JavaScript — for example via encoded javascript: URLs, backslash-based relative URLs resolved as remote hosts, markup-breaking programmatic element/attribute names or HTML comments, raw </textarea> reintroduction through Markdown passthrough, or preserved <style>/<meta http-equiv=refresh>/<base href> tags in custom policies. Most custom-policy issues do not affect the default sanitize=True configuration; they primarily affect helper APIs, programmatic DOM construction, html_passthrough=True, and custom policies/transform pipelines.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00587 48th percentileScored 2026-11-07
Fix Fixed justhtml (EmilStenstrom): 1.15.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Total

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

Affected products

VendorProductAffected versionsFixed inStatusSource
EmilStenstromjusthtmlbefore 1.15.01.15.0Patch availableCNA
  • justhtml VendorEmilStenstrom Affected before 1.15.0 Fixed in 1.15.0 Patch available CNA

Remediation

  • Fix · CNA justhtml (EmilStenstrom) Fixed in 1.15.0

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-5388
  2. 2026-10-03 Alias added: GHSA-9ph2-9r4x-rhjp

References

Advisory 1

  • 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-2026-04066 justhtml before 1.18.0 Denial of Service via CSS Selector CVSS 4.0HIGH 8.7
See all 10 →

Sources

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