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CVE-2026-44307

Path Traversal in Mako (CVE-2026-44307)

Summary

Path traversal in Mako (CVE-2026-44307). Risk of unauthorized operations or information disclosure. Exploitable via Template.__init__. Mitigation: upgrade to 1.3.12 or later.

Original description

The description as published by the source.

Summary

On Windows, a URI using backslash traversal (e.g. \..\..\ secret.txt) bypasses the directory traversal check in Template.__init__ and the posixpath-based normalization in TemplateLookup.get_template(), allowing reads of files outside the configured template directory.

Details

The root cause is a mismatch between posixpath (used for URI normalization in get_template()) and os.path (used for file access via os.path.isfile() and validation via os.path.normpath() in Template.__init__). On Windows, os.path is ntpath, which treats \ as a path separator, while posixpath treats it as a literal character.

The vulnerability chain:

  1. get_template() strips only leading / via re.sub(r"^\/+", "", uri) and normalizes with posixpath — backslash \ is treated as a literal character, so \..\ secret.txt passes through with .. undetected.
  2. Template.__init__() validation uses os.path.normpath() — on Windows this resolves \..\ secret.txt to \secret.txt, which does not start with .., so the startswith("..") check passes.
  3. os.path.isfile() on Windows interprets \ as a path separator, resolving the .. traversal and finding files outside the template directory.

Affected code

  • mako/lookup.py: TemplateLookup.get_template() uses posixpath.normpath/posixpath.join for path construction but os.path.isfile() for existence check
  • mako/template.py: Template.__init__() URI validation uses `os.path.normpath()…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-44307 has been found in Mako.
Attackers can target a specific entry point like Template.__init__ over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade Mako to 1.3.12 or later.
If unsure, ask your IT team or search "Mako CVE-2026-44307" on the vendor's site.

CVE-2026-44307 (Mako) — CWE-22
Attack surface: Template.__init__ / posixpath / os.path / ntpath
Patched: 1.3.12 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Path traversal (CWE-22) exists in Mako. Attackers reach the vulnerable code path via Template.__init__.

📍 Affected scope

Check the vendor advisory for the affected versions of Mako. Attack surface: Template.__init__ / posixpath / os.path / ntpath.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 1.3.12.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Mako' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'Mako' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で Mako を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade Mako to 1.3.12

    ステージング環境で 1.3.12 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

pip Mako
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.12"}]}]
PyPI mako
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.12"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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