CVE-2026-8445

criticalpriority · track · 39EPSS 0.006 · 50 %ileUS
grimoire priorityP2 · Scheduled
Exploitable?
—
no known exploitation
Likely / severe?
0.64% (50th) EPSS
CVSS 9.8 · critical
Is it mine?
1 products
Check your exposure
Who says so?
1 sources
osv

EPSS · scored 2026-10-28

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.

01

cvss

Technical severity, 0–10. One row per scoring source.

9.8
010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · high–critical · 8.1–9.8

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hprimary · disclosure@vulncheck.comexploitability 3.9 · impact 5.9
v4.09.3criticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Xsecondary · disclosure@vulncheck.com
v4.08.1highCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Xsecondary · CVSS-BT (t0sche)
02

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: poc · Automatable: yes · Technical Impact: totalcoordinatorcisa_ssvcUS
03

weaknesses

The CWE weakness classes this flaw belongs to.

04

affected products (1)

Products and version ranges known to be affected.

05

advisories (1)

Vendor and ecosystem advisories describing this.

  • GHSA-3rcm-vjrc-p45jJustHTML has a Sanitizer Bypass (in Markdown)2026-03-18ghsa · osvUS

    ## Summary `to_markdown()` does not sufficiently escape text content that looks like HTML. As a result, untrusted input that is safe in `to_html()` can become raw HTML in Markdown output. This is not specific to tokenizer raw-text states like `<title>`, `<noscript>`, or `<plaintext>`, although those states can trigger the behavior. The root cause is broader: Markdown text serialization leaves angle brackets unescaped in text nodes. ## Details When converting a parsed document to Markdown, text nodes are escaped for a small set of Markdown metacharacters, but HTML-significant characters such as `<` and `>` are preserved. That means content parsed as text, including entity-decoded text or text produced by RCDATA/RAWTEXT-style parsing, can be emitted into Markdown as raw HTML. Examples of affected input include: - Text produced from entity-decoded input such as `&lt;script&gt;...&lt;/script&gt;` - Text inside elements like `<title>`, `<textarea>`, `<noscript>` (when parsed as raw text), and `<plaintext>` This is distinct from actual `<script>` or `<style>` elements in the DOM. Those are already dropped by default in `to_markdown()` unless `html_passthrough=True`. ## Proof of Concept ### General case ```python from justhtml import JustHTML doc = JustHTML("<p>&lt;img src=x onerror=alert(1)&gt;</p>", fragment=True) print(doc.to_html()) print() print(doc.to_markdown())

06

sources

Which sources assert this record, and when.

published 2026-08-23modified 2026-08-26
07

references (2) nvd

External citations — patches, advisories, analysis.

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