Universal Bucket Hijacking exploits the globally unique namespace requirement of Cloud Service Providers (CSPs) such as AWS and GCP. When organizations delete storage buckets but retain "dangling references" in application code, IaC templates, or client-side binaries, attackers can register the identical bucket name. This redirects sensitive data streams—including server logs, user uploads, and backups—directly to attacker-controlled endpoints. Because the traffic is directed toward legitimate CSP domains via HTTPS, the exfiltration bypasses traditional WAF and IDS/IPS detection, leading to critical confidentiality loss and potential supply chain compromise via malicious asset injection.

• Vulnerability Overview: The Global Namespace Risk

  • Exploits the architectural requirement that bucket names must be unique across all tenants within a specific CSP region or globally.
  • Occurs when a resource is decommissioned, but the pointer (URL/name) remains active in production environments or legacy code.
  • Targets "dangling references" frequently discovered in public JavaScript files, mobile app binaries, and leaked Terraform or CloudFormation templates.

• Technical Exploitation Mechanics

  • Reconnaissance: Attackers utilize automated scripts to probe for 404 Not Found responses (indicating the name is available) versus 403 Forbidden (indicating the name is owned).
  • Registration: Once an available referenced name is identified, the attacker claims the bucket within the CSP's console.
  • Data Capture: Attackers configure permissive IAM write policies on the hijacked bucket, allowing the victim's orphaned application to upload data without further authentication.

• Impact and Exfiltration Vectors

  • Data Confidentiality Loss: Direct exfiltration of PII, session tokens, and internal system logs that are automatically streamed to the hijacked endpoint.
  • Supply Chain Integrity: If the hijacked bucket hosted static assets (JS/CSS), attackers can replace legitimate files with malicious payloads to execute XSS or credential theft on the victim's site.
  • Detection Evasion: Traffic remains encrypted via HTTPS and is directed to trusted CSP domains, rendering the attack invisible to most traditional perimeter security tools.

• Detection and Mitigation Strategies

  • Implement synchronized lifecycle management to ensure that bucket deletion is accompanied by the immediate removal of all references in source code and IaC.
  • Monitor application logs for a spike in 404 Not Found errors targeting cloud storage endpoints, which may indicate a dangling reference being probed.
  • Transition from hardcoded bucket strings to centralized configuration management and environment variables to minimize exposure in client-side binaries.

• Conclusion: Systemic Cloud Risk

  • The vulnerability is systemic to the design of cloud namespaces rather than a specific software bug.
  • Security professionals must treat cloud resource identifiers as sensitive assets that require strict deprecation workflows.