CVE-2026-59923
Mistune: XSS via percent-encoded javascript URI bypass in safe_url()
6.1
MEDIUM
CVSS 3.1
EPSS 0.20%
Description
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, HTMLRenderer.safe_url() does not block percent-encoded javascript URIs, allowing attacker-supplied Markdown links or images to bypass URL protections and execute script in rendered HTML. This issue is fixed in version 3.3.0.
How to fix CVE-2026-59923
To remediate CVE-2026-59923, upgrade the affected package to a fixed version below.
- —upgrade to 3.3.0 or later
Is CVE-2026-59923 being exploited?
Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 3.3.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |