What is CVE-2026-44899?

CVE-2026-44899 is a medium-severity vulnerability in Lepture Mistune, classified under Cross-site Scripting. CVSS score: 4.7/10. Published 2026-05-26.

How severe is CVE-2026-44899?

Medium severity. CVSS v3 base score is 4.7 out of 10.

XSS in Lepture Mistune

CVE-2026-44899

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a regex compiled as _num_re = re.compile(r"^\d+(?:\.\d*)?"). When the validated valu…

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.000 (9.3th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.7 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N.

Affected products

Lepture Mistune — versions < 3.2.1
Mistune_project Mistune

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

security-advisories@github.com (Product, x_refsource_MISC, Release Notes)
security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)

Frequently asked questions

What is CVE-2026-44899?: CVE-2026-44899 is a medium-severity vulnerability in Lepture Mistune, classified under Cross-site Scripting. CVSS score: 4.7/10. Published 2026-05-26.
How severe is CVE-2026-44899?: Medium severity. CVSS v3 base score is 4.7 out of 10.