Unit 42 Discloses Universal Bucket Hijacking Flaw Affecting AWS, Google Cloud, and Azure

Executive Summary

Palo Alto Networks' Unit 42 has identified a critical architectural vulnerability, termed "bucket hijacking," that affects major cloud service providers (CSPs), including Amazon Web Services (AWS), Google Cloud (GCP), and Microsoft Azure. This technique exploits the global namespace system for storage buckets, where a bucket's name is a unique identifier across the entire platform. An attacker with permissions to delete a target bucket can intercept active data streams by deleting the original bucket and immediately recreating one with the identical name under an account they control.

This silent redirection of data, such as audit logs, application telemetry, and sensitive business information, poses a severe data exfiltration risk. The attack does not require modification of the data stream's configuration, bypassing typical permissions required for such changes. While Unit 42 has not observed this technique used by threat actors in the wild, its potential for stealthy, high-impact attacks is significant. Organizations are strongly advised to review and harden their Identity and Access Management (IAM) policies, specifically restricting bucket deletion permissions and implementing robust monitoring for such activities.

Vulnerability Details

The bucket hijacking vulnerability stems from a fundamental design choice in modern cloud infrastructure: the use of a global, shared namespace for storage bucket names. When a service, such as Google Cloud Logging or AWS CloudTrail, is configured to stream data to a storage bucket (e.g., an S3 bucket or GCS bucket), the destination is identified solely by its name.

The attack hinges on the separation of permissions between managing a data stream's configuration and managing the destination bucket itself. An attacker does not need permissions to alter the data stream (e.g., logging.sinks.update in GCP). Instead, they only need permissions to delete the target bucket.

The attack flow is as follows:

1. Gain Initial Access: The attacker compromises a cloud environment and obtains IAM credentials with specific permissions.
2. Acquire Permissions: The attacker secures the permissions required to delete the target bucket. In Google Cloud, this would be storage.objects.delete (to empty the bucket first) and storage.bucket.delete.
3. Execute Hijack: The attacker deletes the legitimate bucket. Since the bucket name is now available in the global namespace, they immediately recreate a new bucket with the exact same name but within their own attacker-controlled cloud account.
4. Intercept Data: The existing, unchanged data stream configuration automatically begins routing all new data to the attacker's bucket, believing it is the original destination. This results in the silent exfiltration of all data processed by the stream from that point forward.

This method is particularly insidious because the data stream service itself remains unaltered and may not generate any errors, leading to a prolonged and undetected data breach.

Affected Systems

The research from Unit 42 confirms this architectural flaw impacts multiple services across the three largest cloud providers. While the principle is universal, specific services tested and confirmed to be vulnerable include:

• Google Cloud Platform (GCP):
  • Google Cloud Logging sinks
  • Pub/Sub subscriptions pushing to storage
  • Storage Transfer Service jobs
• Amazon Web Services (AWS):
  • Services that stream data to S3 buckets (e.g., CloudTrail, VPC Flow Logs, ELB access logs).
• Microsoft Azure:
  • Services that stream data to Azure Blob Storage containers.

Essentially, any cloud service that uses a bucket name as the sole identifier for a data stream destination is potentially vulnerable. The risk is not limited to logging services but extends to data pipelines, backup processes, and any automated data transfer mechanism.

Exploitation Status

As of the publication of the research on June 22, 2026, Unit 42 has not identified any instances of this bucket hijacking technique being used by threat actors in the wild. However, the disclosure of this method significantly increases the likelihood that it will be incorporated into the toolkits of cloud-focused threat actors. Its stealth and high potential for impact make it an attractive vector for espionage and data theft. The low barrier to entry—requiring only delete permissions rather than high-level administrative access—further elevates the risk.

Given the difficulty in detecting this attack post-facto, organizations should treat this as a high-priority, proactive mitigation scenario rather than waiting for evidence of active exploitation.

Impact Assessment

The business impact of a successful bucket hijacking attack is severe and multifaceted:

• Data Exfiltration: The primary impact is the theft of sensitive information. This could include customer PII, financial records, intellectual property, application logs containing credentials or tokens, and critical infrastructure telemetry.
• Compliance and Regulatory Violations: The exfiltration of regulated data (e.g., GDPR, HIPAA, PCI-DSS) can lead to massive fines, legal action, and reputational damage. The loss of audit logs can itself be a compliance failure.
• Loss of Visibility: If the hijacked data stream consists of security logs (e.g., CloudTrail, VPC Flow Logs), the organization loses critical visibility into its own environment. This blinds security teams to other malicious activities, effectively creating a backdoor for the attacker to operate undetected.
• Reconnaissance for Future Attacks: By intercepting logs and operational data, an attacker can gather detailed intelligence about the victim's infrastructure, applications, and user behavior to plan more sophisticated, targeted attacks.

Because the attack is silent and does not disrupt service availability, it can persist for long periods, leading to a catastrophic and continuous data breach.

IOCs — Directly from Articles

No Indicators of Compromise (IOCs) were provided in the source article, as this technique has not yet been observed in a real-world attack.

Cyber Observables — Hunting Hints

Security teams can proactively hunt for activity related to this technique. The following patterns could indicate preparatory or active bucket hijacking attempts:

Detection & Response

Detecting this attack requires moving beyond simple error monitoring and focusing on the lifecycle of critical cloud resources. Effective detection and response strategies include:

1. Audit Log Monitoring: Implement real-time monitoring and alerting on specific, high-risk API calls. Create high-severity alerts for the deletion of any bucket that is a known data sink. In GCP, this is the storage.buckets.delete event. In AWS, it's s3:DeleteBucket via CloudTrail. These alerts should trigger an immediate investigation.

2. Permission Change Auditing: Monitor for any changes to IAM policies that grant storage.bucket.delete or s3:DeleteBucket permissions. Such changes should require a justification and approval process.

3. Configuration Drift Detection: Regularly run automated checks to validate that the account/project ID of a destination bucket matches the account/project ID of the data stream source. Any mismatch is a red flag for a successful hijack. This can be achieved with custom scripts or a Cloud Security Posture Management (CSPM) tool.

4. D3FEND Techniques for Detection:

   • Network Traffic Analysis (D3-NTA): While the stream configuration doesn't change, post-hijack data flows to a new, external endpoint. Monitoring network egress from the cloud service generating the data might reveal traffic to an unexpected attacker-owned account, although this can be difficult to distinguish.
   • File Analysis (D3-FA): In this context, analyzing cloud audit logs for the specific sequence of DeleteBucket followed by successful writes from the same data stream is the most effective detection method.

Response Plan: If a hijack is suspected, the immediate response should be to disable the data stream to stop the data leakage. Then, investigate the account that now owns the bucket and analyze audit logs to determine who deleted the original bucket and when. Finally, recreate the bucket under the correct account and re-enable the data stream after ensuring the compromising permissions have been revoked.

Mitigation

Mitigation focuses on proactive hardening and the principle of least privilege.

1. Strict IAM Policies (M1026 - Privileged Account Management): This is the most critical mitigation. The permission to delete storage buckets (storage.bucket.delete, s3:DeleteBucket) is highly destructive and should be denied by default. Only grant it to a very small number of trusted administrative roles, and even then, require multi-factor authentication for its use. Avoid using wildcard permissions like storage.*.

2. Use Resource Locks (M1054 - Software Configuration): All major CSPs provide mechanisms to prevent the accidental or malicious deletion of critical resources.

   • AWS: Enable Termination Protection on CloudFormation stacks that define S3 buckets. Use S3 Object Lock in compliance mode to make data immutable, which can also prevent bucket deletion under certain conditions.
   • Google Cloud: Apply a Bucket Lock to implement a retention policy, which prevents the deletion of the bucket until the lock is removed.
   • Azure: Use Resource Locks (CanNotDelete or ReadOnly) on the storage account or container to prevent deletion.

3. Regular Audits (M1047 - Audit): Continuously audit and review all IAM roles and policies to ensure least privilege is maintained. Use automated tools to identify and alert on roles with excessive permissions, especially those related to resource deletion.

4. Decouple Permissions: Ensure that roles responsible for day-to-day operations do not have permissions to delete shared infrastructure resources like data stream destination buckets. Separate duties between application/service owners and infrastructure administrators.

By combining these strategies, organizations can significantly reduce their exposure to this novel and dangerous attack vector.