GHSA-v92g-xgxw-vvmm

7.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N CVSS Calculator
7.7 (High) CVSS_V4 - 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 CVSS Calculator

Summary

Mako: Path traversal via double-slash URI prefix in TemplateLookup

Details

Summary

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:

Template.__init__ strips one leading / using if/slice
TemplateLookup.get_template() strips all leading / using re.sub(r"^\/+", "")

When a URI like //../../../../etc/passwd is passed: 1. get_template() strips all / → ../../../../etc/passwd → file found via posixpath.join(dir_, u) 2. Template.__init__ strips one / → /../../../../etc/passwd → normpath → /etc/passwd 3. /etc/passwd.startswith(..) → False → check bypassed

Impact

Arbitrary 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().

Note: 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.

Fix

Changed Template.__init__ to use lstrip("/") instead of stripping only a single leading slash, so both code paths handle leading slashes consistently.

Database specific

{
    "nvd_published_at": "2026-04-23T19:17:29Z",
    "cwe_ids": [
        "CWE-22"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-16T21:16:40Z",
    "severity": "HIGH"
}

References

Affected packages

PyPI / mako

Package

Name: mako; View open source insights on deps.dev
Purl: pkg:pypi/mako

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Fixed

1.3.11

Affected versions

0.*

0.1.0

0.1.1

0.1.2

0.1.3

0.1.4

0.1.5

0.1.6

0.1.7

0.1.8

0.1.9

0.1.10

0.2.0

0.2.1

0.2.2

0.2.3

0.2.4

0.2.5

0.3.0

0.3.1

0.3.2

0.3.3

0.3.4

0.3.5

0.3.6

0.4.0

0.4.1

0.4.2

0.5.0

0.6.0

0.6.1

0.6.2

0.7.0

0.7.1

0.7.2

0.7.3

0.8.0

0.8.1

0.9.0

0.9.1

1.*

1.0.0

1.0.1

1.0.2

1.0.3

1.0.4

1.0.5

1.0.6

1.0.7

1.0.8

1.0.9

1.0.10

1.0.11

1.0.12

1.0.13

1.0.14

1.1.0

1.1.1

1.1.2

1.1.3

1.1.4

1.1.5

1.1.6

1.2.0

1.2.1

1.2.2

1.2.3

1.2.4

1.3.0

1.3.1

1.3.2

1.3.3

1.3.4

1.3.5

1.3.6

1.3.7

1.3.8

1.3.9

1.3.10

Database specific

last_known_affected_version_range

"<= 1.3.10"

source

"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-v92g-xgxw-vvmm/GHSA-v92g-xgxw-vvmm.json"