High‑Severity Unrestricted File Upload in Drupal Core (CVE‑2020‑13671)
What It Is
Drupal core versions prior to the 2020‑09‑02 patch contain an improper sanitization flaw in file‑extension handling. An attacker can upload a file with a crafted extension, bypassing validation and achieving arbitrary code execution on the web server.
Exploitability
The vulnerability is rated CVSS 3.1 8.8 (High) and is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Public proof‑of‑concept code exists, and limited threat‑actor activity has been observed targeting unpatched Drupal sites.
Affected Products
- Vendor: Drupal
- Products: Drupal core (all supported major versions prior to the September 2020 security release)
Why It Matters for Compliance & Audit Readiness
Unrestricted file upload defeats fundamental access‑control safeguards and erodes the evidentiary trail required for auditability. For organizations subject to frameworks such as NIST CSF, ISO 27001, or PCI‑DSS, the flaw directly impacts the “Protect – Access Control” and “Detect – Continuous Monitoring” functions. Demonstrating timely patch management, validated file‑upload controls, and documented remediation steps provides defensible proof of due diligence during audits and strengthens vendor‑management assurance.
Recommended Actions
- Patch Immediately: Upgrade to the patched Drupal core release (e.g., 8.9.13, 9.0.7, or later). Verify the version via the site’s status report.
- Validate File‑Upload Controls: Enforce strict whitelist of allowed extensions, enable MIME‑type verification, and store uploads outside the web root when possible.
- Log & Monitor: Enable detailed upload logging, alert on anomalous file types, and integrate with SIEM for real‑time detection.
- Document Remediation: Record patch version, configuration changes, and monitoring rules in your CMDB and control‑mapping repository to support audit evidence.
- Review Vendor‑Management Process: Ensure third‑party components (e.g., contributed modules) are also assessed for similar upload weaknesses.
Source: https://nvd.nist.gov/vuln/detail/CVE-2020-13671