XSS in Emilstenstrom Justhtml
CVE-2026-8445
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. <script>) 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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.006 (48.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 48.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.006 · change: +0.003
Affected products
Weakness classification (CWE)
References
- github.com/EmilStenstrom/justhtml/security/advisories/GHSA-3rcm-vjrc-p45j (vendor-advisory)
- www.vulncheck.com/advisories/justhtml-before-sanitizer-bypass-via-markdown (third-party-advisory)
Frequently asked questions
- What is CVE-2026-8445?
- CVE-2026-8445 is a critical-severity vulnerability in Emilstenstrom Justhtml, classified under Cross-site Scripting. CVSS score: 9.8/10. Published 2026-08-23.
- How severe is CVE-2026-8445?
- Critical severity. CVSS v3 base score is 9.8 out of 10.