CVE-2026-41205: Mako Path Traversal Vulnerability
HIGHCVE-2026-41205 is a HIGH (CVSS 7.5) path traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Mako libraries in the PyPI ecosystem. The issue involves path traversal via double-slash uri prefix in templatelookup. Remediation is available by upgrading affected packages to version 1.3.11.
CVE-2026-41205 at a Glance
Security Impact
CVSS: 7.5
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).
How to Fix CVE-2026-41205
To remediate this vulnerability, upgrade all affected Mako dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
pip install Mako>=1.3.11Run the following command in your project directory to verify that all resolved dependencies use the patched release:
pip show MakoHow to Check if You Are Affected
To determine whether your Python environment is affected by CVE-2026-41205, inspect your installed packages using pip:
pip show MakoAnalyze the terminal output to locate any version of Mako in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.3.11), your application is affected.
Note: The pip show Mako command checks currently installed packages in your active Python environment.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. In Mako, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-41205 Affected Mako Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
Mako
|
PyPI |
< 1.3.11
|
1.3.11
|
References
Frequently Asked Questions
What is CVE-2026-41205?
Which Mako versions are affected?
What version fixes CVE-2026-41205?
Is Mako affected?
What is the CVSS score of CVE-2026-41205?
What CWE is associated with CVE-2026-41205?
How can I check PyPI dependencies for CVE-2026-41205?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-v92g-xgxw-vvmm",
"modified" : "2026-06-05T14:13:04Z",
"published" : "2026-04-16T21:16:40Z",
"aliases" : [ "CVE-2026-41205" ],
"summary" : "Mako: Path traversal via double-slash URI prefix in TemplateLookup",
"details" : "### Summary\n\n`TemplateLookup.get_template()` is vulnerable to path traversal when a URI starts with `//` (e.g., `//../../../secret.txt`). The root cause is an inconsistency between two slash-stripping implementations:\n\n- `Template.__init__` strips **one** leading `/` using `if`/slice\n- `TemplateLookup.get_template()` strips **all** leading `/` using `re.sub(r\"^\\/+\", \"\")`\n\nWhen a URI like `//../../../../etc/passwd` is passed:\n1. `get_template()` strips all `/` → `../../../../etc/passwd` → file found via `posixpath.join(dir_, u)`\n2. `Template.__init__` strips one `/` → `/../../../../etc/passwd` → `normpath` → `/etc/passwd`\n3. `/etc/passwd`.startswith(`..`) → `False` → **check bypassed**\n\n### Impact\n\nArbitrary file read: any file readable by the process can be returned as rendered template content when an application passes untrusted input directly to `TemplateLookup.get_template()`.\n\nNote: this is exploitable at the library API level. HTTP-based exploitation is mitigated by Python's `BaseHTTPRequestHandler` which normalizes double-slash prefixes since CPython gh-87389. Applications using other HTTP servers that do not normalize paths may be affected.\n\n### Fix\n\nChanged `Template.__init__` to use `lstrip(\"/\")` instead of stripping only a single leading slash, so both code paths handle leading slashes consistently.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"
}, {
"type" : "CVSS_V4",
"score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:P"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "PyPI",
"name" : "Mako"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "1.3.11"
} ]
} ],
"database_specific" : {
"last_known_affected_version_range" : "<= 1.3.10"
}
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/sqlalchemy/mako/security/advisories/GHSA-v92g-xgxw-vvmm"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-41205"
}, {
"type" : "WEB",
"url" : "https://github.com/sqlalchemy/mako/commit/e05ac61989a7fb9dd7dcde6cfd72dc48328719a3"
}, {
"type" : "WEB",
"url" : "https://github.com/pypa/advisory-database/tree/main/vulns/mako/PYSEC-2026-88.yaml"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/sqlalchemy/mako"
}, {
"type" : "WEB",
"url" : "https://github.com/sqlalchemy/mako/releases/tag/rel_1_3_11"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-22" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2026-04-16T21:16:40Z",
"nvd_published_at" : "2026-04-23T19:17:29Z"
}
}