CVE-2026-59923CWE-79

Mistune: XSS via percent-encoded javascript URI bypass in safe_url()

Medium · published July 8, 2026

CVSS v3.1
6.1
EPSS
0%
Percentile
27.2
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.1 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00348 · 27.2th percentile
Weakness
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-07-08T16:14Z
EPSS history
Timeline
  • 08 JUL 16:14Z
    Mistune: XSS via percent-encoded javascript URI bypass in safe_url()
    cvelistv5