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CVE-2026-5388

CVE-2026-5388 · justhtml before 1.15.0 Multiple Security Issues

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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.

CVSS 9.3 · Critical · EPSS 0.6% · Fix available

Published
Updated

Stack: python

Affected products and versions

  • justhtml

    Versions
    • ≥ 0, < 1.15.0: Affected (semver)
    • 1.15.0: Not affected (semver)

    Update to 1.15.0

  • justhtml PyPI

    Versions
    • 0.1.0
    • 0.10.0
    • 0.11.0
    • 0.12.0
    • 0.13.0
    • 0.13.1
    • 0.14.0
    • 0.15.0
    • 0.16.0
    • 0.17.0
    • 0.18.0
    • 0.19.0
    • 0.2.0
    • 0.20.0
    • 0.21.0
    • 0.22.0
    • 0.23.0
    • 0.24.0
    • 0.25.0
    • 0.26.0
    • 0.27.0
    • 0.28.0
    • 0.29.0
    • 0.3.0
    • 0.30.0
    • 0.31.0
    • 0.32.0
    • 0.33.0
    • 0.34.0
    • 0.35.0
    • 0.36.0
    • 0.37.0
    • 0.38.0
    • 0.39.0
    • 0.4.0
    • 0.40.0
    • 0.5.0
    • 0.5.1
    • 0.5.2
    • 0.6.0
    • 0.7.0
    • 0.8.0
    • 0.9.0
    • 1.0.0
    • 1.1.0
    • 1.10.0
    • 1.11.0
    • 1.12.0
    • 1.13.0
    • 1.14.0
    • 1.2.0
    • 1.3.0
    • 1.4.0
    • 1.5.0
    • 1.6.0
    • 1.7.0
    • 1.8.0
    • 1.9.0
    • 1.9.1
    Affected ranges
    • ECOSYSTEM: < 1.15.0

    Update to 1.15.0

Original sources

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