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CVE-2026-41205 high CVSS 7.5

Path Traversal in Mako (CVE-2026-41205)

Summary

Path traversal in Mako (CVE-2026-41205). Confidential information can be exposed externally. Exploitable via Template.__init__. Mitigation: upgrade to 1.3.11 or later.

Original description

The description as published by the source.

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.

Source: GitHub Security Advisories (Global) 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-2026-41205 has been found in Mako.
Attackers can target a specific entry point like Template.__init__ over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.5/10.
What to do: upgrade Mako to 1.3.11 or later.
If unsure, ask your IT team or search "Mako CVE-2026-41205" on the vendor's site.

CVE-2026-41205 (Mako) — CWE-22 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Template.__init__ / normpath / False / BaseHTTPRequestHandler
Patched: 1.3.11 — 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__ without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of Mako. Attack surface: Template.__init__ / normpath / False / BaseHTTPRequestHandler.

🔥 Severity

Severity: High (CVSS 7.5/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 1.3.11.

🛡️ 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 1.3.11

    ステージング環境で 1.3.11 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":"1.3.11"}]}]
PyPI mako
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.11"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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