XSS in Lepture Mistune
CVE-2026-59929
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the safe_url filter in src/mistune/renderers/html.py blocks only javascript:, vbscript:, file:, and data: schemes, allowing legacy or chained schemes such as feed:, view-source:, jar:, livescript:, mocha:, ms-its:, mk:, and res: to reach rendered href and src attributes and potentially execute script in affected user agents. This issue is fixed in version 3.3.0.
Vulnerability class: XSS (Cross-Site Scripting)
EPSS: 0.002 (13.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
Affected products
- Lepture Mistune — versions < 3.3.0
- Mistune_project Mistune
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Third Party Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-59929?
- CVE-2026-59929 is a medium-severity vulnerability in Lepture Mistune, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-07-08.
- How severe is CVE-2026-59929?
- Medium severity. CVSS v3 base score is 6.1 out of 10.