RCE in Lepture Mistune
CVE-2026-115351
Mistune from 3.2.1 before 3.3.0 contains a CSS injection vulnerability that allows attackers controlling markdown input to inject arbitrary style declarations via the unvalidated figwidth option of the figure directive. Attackers can append declarations like background:url() to the rendered figure style attribute, forcing victim browsers to send requests to attacker servers and leak attribute values.
Vulnerability class: RCE (Remote Code Execution)
Published · last modified .
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.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/lepture/mistune/security/advisories/GHSA-xmwc-wjpr-q378 (vendor-advisory)
- www.vulncheck.com/advisories/mistune-3.2.1-before-3.3.0-css-injection-via-figur… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-115351?
- CVE-2026-115351 is a medium-severity vulnerability in Lepture Mistune, classified under Code Injection. CVSS score: 4.7/10. Published 2026-10-22.
- How severe is CVE-2026-115351?
- Medium severity. CVSS v3 base score is 4.7 out of 10.