Read the docs
TI-2026-07422 Aliases CVE-2026-8445GHSA-wf6m-786j-gxrr

justhtml before 1.12.0 Sanitizer Bypass via Markdown

Priority HIGH 81CWE-79Published · Updated

Key facts

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

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

Summary

justhtml versions <= 1.11.0 (fixed in 1.12.0) do not sufficiently escape HTML-significant characters (angle brackets) in text nodes when converting a parsed document to Markdown via to_markdown(). While a small set of Markdown metacharacters are escaped, characters such as < and > are preserved, so untrusted input that is safe in to_html() — including entity-decoded text (e.g. &lt;script&gt;) or text from RCDATA/RAWTEXT-parsed elements like <title>, <textarea>, <noscript>, and <plaintext> — can be emitted as raw HTML in the Markdown output, enabling a sanitizer bypass and potential cross-site scripting when that output is rendered.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00635 50th percentileScored 2026-11-07
Fix Fixed justhtml (EmilStenstrom): 1.12.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
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 1.12.01.12.0Patch availableCNA
  • justhtml VendorEmilStenstrom Affected before 1.12.0 Fixed in 1.12.0 Patch available CNA

Remediation

  • Fix · CNA justhtml (EmilStenstrom) Fixed in 1.12.0

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    EmilStenstrom justhtml 1.12.0

    2 records Highest priority Priority HIGH 1 HIGH, 1 LOW

    Other records, highest priority first

    • TI-2026-07586 justhtml before 1.12.0 Mutation XSS via Raw Text ElementsPriority LOW 23
    Show all 2 records →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-8445
  2. 2026-10-03 Alias added: GHSA-wf6m-786j-gxrr
  3. 2026-10-25 EPSS moved to the 50th–90th percentile

References

Advisory 1

  • 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
  • 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