Severity rationale: While not yet observed in the wild, the technique provides a silent, reliable method for data exfiltration and log suppression across all major cloud providers.
Universal Bucket Hijacking Technique Enables Stealthy Cloud Data Exfiltration
Palo Alto Networks · Cloud Storage Services (Multiple)
A newly detailed cloud hijacking technique allows attackers to intercept sensitive data streams, such as audit logs, by exploiting the global uniqueness of storage bucket names. By deleting and recreating a bucket under their own control, attackers can silently redirect automated data flows from your environment to theirs without changing your service configurations.
Key Facts
- Vendor
- Palo Alto Networks
- Product
- Cloud Storage Services (Multiple)
- Exploitation
- No exploitation observed
- Affected versions
- AWS S3 (Pre-mitigation), Google Cloud Storage / Logging Sinks (Pre-mitigation), Azure Storage (Pre-mitigation)
Summary
A "Universal Bucket Hijacking" technique has been identified that allows attackers to redirect cloud data streams—including audit logs and sensitive telemetry—to attacker-controlled environments. By exploiting the global uniqueness of storage bucket names across Amazon Web Services (AWS), Google Cloud Platform (GCP), and Microsoft Azure, an attacker with sufficient permissions to delete a bucket can recreate it under their own account to intercept automated data flows.
What happened
Research from Unit 42 revealed a fundamental architectural risk in how cloud services handle automated data streams. Many cloud services (like GCP Cloud Logging Sinks or AWS S3 Replication) are configured to "push" data to a destination bucket based on its name. Because bucket names are globally unique, if an attacker obtains the permissions to delete a target bucket (e.g., storage.buckets.delete), they can immediately recreate a bucket with the exact same name in an external, attacker-controlled tenant.
The cloud service, still configured to send data to that specific name, begins delivering data to the new bucket located in the attacker's environment. This transition is often silent; the original configuration (the "sink" or "replication rule") remains pointed at the correct name, but the underlying owner of that name has changed.
Why it matters
This technique enables high-stealth data exfiltration. Because the configuration on the victim's side appears intact, traditional configuration monitoring might not trigger an alert. If an attacker hijacks a logging sink, they not only steal sensitive metadata but also blind the security team by intercepting the very logs used for detection. This poses a systemic risk to forensic integrity and data privacy across all major CSPs.
Affected systems
- Google Cloud: Cloud Logging Sinks, Pub/Sub subscriptions (GCS push), Storage Transfer Service.
- AWS: S3 Bucket Replication and other services targeting S3 buckets by name.
- Microsoft Azure: Services utilizing globally unique storage account names for data exports.
Recommended actions
Cloud providers have been notified and are working on or have implemented platform-level mitigations (such as requiring destination account ID verification). However, defenders should take the following steps:
- Restrict Permissive IAM: Audit and restrict
deletepermissions for storage buckets. These should be treated as high-privilege credentials. - Monitor for Bucket Recreation: Set up alerts for
DeleteBucketevents followed quickly by a change in bucket ownership or the inability to access a previously owned bucket name. - Enforce Account ID Validation: For AWS S3 Replication, ensure you are using the
ExpectedBucketOwnerparameter to prevent data from being sent to a bucket owned by an unauthorized account. - Audit Logging Sinks: Periodically verify that the destination buckets for critical logs are residing within known, authorized organization projects or accounts.
Technical details
The vulnerability stems from the 'Global Namespace' design of cloud storage. Multiple cloud services route data to buckets based on the bucket's string name (e.g., 'company-audit-logs'). If an attacker gains the privilege to delete 'company-audit-logs' in the victim account, they can immediately register that same name in an attacker-controlled account. Cloud services currently 'pushing' to that name may fail to verify the underlying Account ID/Project ID of the recipient, continuing to deliver data to the attacker-owned instance of the named bucket.
Detection & hunting
Hunting Queries & Logic
- Log Location: Cloud Audit Logs (AWS CloudTrail, GCP Admin Activity, Azure Activity Logs)
- Suspicious Activity: Look for high-privilege IAM users or service accounts performing
DeleteBucketorstorage.buckets.deleteoperations on buckets that are known destinations for Logging Sinks or Pub/Sub topics. - External Access: Monitor for
SetBucketPolicyor IAM changes on newly created buckets that permit access to external, non-organizational principals. - Orphaned Sinks: Identify logging sinks or data export rules where the destination bucket no longer exists within the organization's resource hierarchy.
Recommended actions
Immediate Containment & Verification
- Audit IAM policies to restrict 'Delete' permissions on all buckets used as destinations for logs or data streams.
- Verify that existing logging sinks and data exports are delivering data to buckets owned by your organization.
Patch & Verify
- Implement 'Expected Bucket Owner' checks in AWS S3 and similar identity-verification features in GCP and Azure.
Hardening
- Enable MFA Delete on critical buckets to prevent unauthorized deletion even if credentials are compromised.
- Use Service Control Policies (SCPs) to prevent the deletion of critical logging buckets across the entire organization.
Sources
Disclaimer: CyberBrief HQ articles are for informational purposes only and do not constitute security advice for any specific environment. Always validate guidance against your own controls and vendor advisories before acting.