CVE-2026-102991 Mako: Path traversal via drive-letter URI on Windows in TemplateLookup
Attackers can exploit path traversal in Mako on Windows to read arbitrary files or execute code via crafted template URIs.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-102991?
CVE-2026-102991 is a medium-severity path traversal vulnerability in sqlalchemy mako, published on 30 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Mako is a template library written in Python. Prior to 1.4.2, on Windows, TemplateLookup.get_template() in mako/lookup.py resolves template URIs with posixpath, while Template.__init__() in mako/template.py validates them with os.path, which uses ntpath. A URI beginning with a drive designator causes ntpath to absorb the traversal segments before the leading dot-dot check, while posixpath resolution can escape the configured template directory. An application that passes attacker-controlled template names or include paths can disclose process-readable files on the same volume, and a targeted file containing Mako template syntax may also be parsed and executed as a template. Raw URL paths are generally normalized before reaching this form, but query strings, form or JSON bodies, route parameters, and dynamic include expressions can preserve it. This issue is fixed in version 1.4.2.
Weakness: CWE-22
Which versions are affected by CVE-2026-102991?
3 open source packages ship an affected version, including mako and Mako.
| Package | Affected | Fixed in |
|---|---|---|
mako PyPI | All versions | 1.4.2 |
mako PyPI | All versions | 1.4.2 |
Mako PyPI | All versions | 1.4.2 |
How do I fix CVE-2026-102991?
Upgrade mako to 1.4.2 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-102991 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-102991 exists.
Sources
Also known as AZL-105645, CLEANSTART-2026-RY75386, CLEANSTART-2026-XA70442, ECHO-ad96-000e-33ae, GHSA-5639-2j2p-m4mx, MINI-56m4-2j5m-wh29 and 8 more.