Vulnerability · Published Oct 22, 2026 · Assigned by VulnCheck
CVE-2026-115355Mistune before 3.3.0 Path Traversal and XSS via Include Directive
High 7.5
In plain English
A high-severity path traversal in mistune from lepture. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Mistune before 3.3.0 contains a path traversal vulnerability in the Include directive that allows attackers to read arbitrary files by supplying ../ sequences in include paths. Attackers can also inject HTML through unescaped error messages and included file contents to perform cross-site scripting even when escape=True is set.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | mistune | no fix listed | DEBIAN-CVE-2026-115355 |
| Debian:13 | mistune | no fix listed | DEBIAN-CVE-2026-115355 |
| Debian:14 | mistune | no fix listed | DEBIAN-CVE-2026-115355 |
| PyPI | mistune | 3.3.0 | GHSA-h7ww-273w-6cm8 |
| Ubuntu:22.04:LTS | mistune | no fix listed | UBUNTU-CVE-2026-115355 |
| Ubuntu:24.04:LTS | mistune | no fix listed | UBUNTU-CVE-2026-115355 |
| Ubuntu:26.04:LTS | mistune | no fix listed | UBUNTU-CVE-2026-115355 |
| Ubuntu:26.10 | mistune | no fix listed | UBUNTU-CVE-2026-115355 |
Affected products (as reported)
Weakness: CWE-22 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
References
- GitHub Security Advisory (GHSA-h7ww-273w-6cm8) vendor-advisory
- VulnCheck Advisory: Mistune before 3.3.0 Path Traversal and XSS via Include Directive third-party-advisory