{"id":"CVE-2026-5388","summary":"justhtml before 1.15.0 Multiple Security Issues","details":"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 \u003c/textarea\u003e reintroduction through Markdown passthrough, or preserved \u003cstyle\u003e/\u003cmeta http-equiv=refresh\u003e/\u003cbase href\u003e 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.","aliases":["GHSA-c9vm-hv86-f23r"],"modified":"2026-08-25T04:03:22.240919715Z","published":"2026-08-23T13:34:09.169Z","database_specific":{"cna_assigner":"VulnCheck","cwe_ids":["CWE-20"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5388.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5388.json"},{"type":"ADVISORY","url":"https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-c9vm-hv86-f23r"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-5388"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/justhtml-before-multiple-security-issues"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/emilstenstrom/justhtml","events":[{"introduced":"0"},{"fixed":"c8161901e50de91ad7e09ede7baa158181ef466e"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"1.15.0"}],"source":["AFFECTED_FIELD","DESCRIPTION"]}}],"versions":["v1.14.0","v1.13.0","v1.12.0","v1.11.0","v1.10.0","v1.9.1","v1.9.0","v1.8.0","v1.7.0","v1.6.0","v1.5.0","v1.4.0","v1.3.0","v1.2.0","v1.1.0","v1.0.0","v0.40.0","v0.39.0","v0.38.0","v0.37.0","v0.36.0","v0.35.0","v0.34.0","v0.33.0","v0.32.0","v0.31.0","v0.30.0","v0.29.0","v0.28.0","v0.27.0","v0.26.0","v0.25.0","v0.24.0","v0.23.0","v0.22.0","v0.21.0","v0.20.0","v0.19.0","v0.18.0","v0.17.0","v0.16.0","v0.15.0","v0.14.0","v0.13.1","v0.13.0","v0.12.0","v0.11.0","v0.10.0","v0.9.0","v0.8.0","v0.7.0","v0.6.0","v0.5.2","v0.5.1","v0.5.0","v0.4.0","v0.3.0","v0.2.0","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-5388.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"}]}