Vulnerability · Published Sep 30, 2026 · Assigned by GitHub_M
CVE-2026-102991Mako: Path traversal via drive-letter URI on Windows in TemplateLookup
Medium 6.5
In plain English
A medium-severity path traversal in mako from sqlalchemy. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 29% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | mako | 1.4.2 | GHSA-5639-2j2p-m4mx |
| PyPI | mako | 1.4.2 | PYSEC-2026-4243 |
| Ubuntu:22.04:LTS | mako | no fix listed | UBUNTU-CVE-2026-102991 |
| Ubuntu:24.04:LTS | mako | no fix listed | UBUNTU-CVE-2026-102991 |
| Ubuntu:26.04:LTS | mako | no fix listed | UBUNTU-CVE-2026-102991 |
| Ubuntu:26.10 | mako | no fix listed | UBUNTU-CVE-2026-102991 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| sqlalchemy | mako | < 1.4.2 |
Weakness: CWE-22 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
References
- https://github.com/sqlalchemy/mako/security/advisories/GHSA-5639-2j2p-m4mx x_refsource_CONFIRM
- https://github.com/sqlalchemy/mako/issues/441 x_refsource_MISC
- https://github.com/sqlalchemy/mako/commit/000ed85e4e48771eff460bf4fc721fb43de80e08 x_refsource_MISC
- https://github.com/sqlalchemy/mako/releases/tag/rel_1_4_2 x_refsource_MISC