Full Report
The cloud environment had an API for generating API keys. This had a CSRF vulnerability, mainly because it used a GET request to create the API keys. This ALSO worked with the admin user. By itself, this doesn't have much impact, though. Upon looking deeper into the application, they realized that CORS was misconfigured. In this case, the origin was simply reflected, and credentials were sent. The combination of these two meant that the generated key from above could be stolen. Pretty good impact! The application had a super simple proxy feature with no input validation. Using this method, it was possible to call the AWS metadata endpoint to steal AWS credentials. With the credentials, they decided to figure out what the API had access to. While describing the other EC2 instances, they found passwords in plaintext but I'm unsure what fields these were in. One of the credentials allowed for admin access, allowing for privilege escalation to the AWS Administrator. Overall, a group of super serious bugs leads to complete compromise. This is why defense-in-depth is so essential!
Analysis Summary
# Incident Report: Multi-Stage Cloud Compromise via Chain of Web Vulnerabilities
## Executive Summary
A cloud environment was completely compromised through a sophisticated chain of vulnerabilities, starting with a CSRF flaw and culminating in full AWS Administrator privileges. By combining misconfigured CORS policies, SSRF via an unvalidated proxy, and insecure credential storage, the attacker bypassed initial security controls. The incident highlights the catastrophic potential of "low-impact" bugs when combined and the critical need for defense-in-depth.
## Incident Details
- **Discovery Date:** Not disclosed
- **Incident Date:** Not disclosed
- **Affected Organization:** Not disclosed
- **Sector:** Technology / Cloud Services
- **Geography:** Global / Cloud-based
## Timeline of Events
### Initial Access
- **Date/Time:** T-0
- **Vector:** Cross-Site Request Forgery (CSRF) & CORS Misconfiguration
- **Details:** The attacker exploited a GET-based API key generation endpoint. By leveraging a reflected CORS origin policy that allowed credentials, the attacker successfully triggered API key generation on behalf of an administrator and exfiltrated the resulting key.
### Lateral Movement
- **Date/Time:** T+1
- **Method:** Server-Side Request Forgery (SSRF)
- **Details:** The attacker utilized a simplified proxy feature lacking input validation to query the AWS Metadata Service (IMDS). This allowed for the theft of temporary EC2 IAM role credentials.
### Data Exfiltration/Impact
- **Date/Time:** T+2
- **Details:** Using the stolen IAM credentials, the attacker performed reconnaissance on the EC2 environment. They discovered plaintext passwords stored within EC2 instance metadata/tags (specific fields not identified), which provided administrative access to the broader AWS environment.
### Detection & Response
- **How it was discovered:** Security research/Audit (implied).
- **Response actions taken:** Analysis of the vulnerability chain and identification of the "defense-in-depth" failures.
## Attack Methodology
- **Initial Access:** CSRF via GET request on API key generation endpoint.
- **Persistence:** Generation of valid, long-lived API keys.
- **Privilege Escalation:** Escalation from a standard user/admin session to AWS Administrator via plaintext credential discovery.
- **Defense Evasion:** Use of legitimate (though misconfigured) application proxies to mask internal requests.
- **Credential Access:** Exfiltration of API keys via CORS exploitation and theft of AWS credentials via SSRF.
- **Discovery:** Enumeration of EC2 instances and metadata fields.
- **Lateral Movement:** Pivoting from web application vulnerabilities to cloud infrastructure management.
- **Collection:** Gathering plaintext passwords from environment configurations.
- **Exfiltration:** Transfer of generated API keys and AWS session tokens.
- **Impact:** Total compromise of the AWS cloud organization.
## Impact Assessment
- **Financial:** Not disclosed, but potentially catastrophic due to full cloud control.
- **Data Breach:** Compromise of administrative API keys and plaintext passwords.
- **Operational:** Complete control over the AWS infrastructure, including the ability to shut down or modify all EC2 instances.
- **Reputational:** High; demonstrates significant architectural security failures.
## Indicators of Compromise
- **Network indicators:** Requests to internal metadata IP `169.254.169.254` originating from the application proxy.
- **File indicators:** N/A (Cloud/API based).
- **Behavioral indicators:** Unusual GET requests to API key generation endpoints; cross-origin requests from unauthorized or reflected domains; unexpected `DescribeInstances` API calls from EC2 IAM roles.
## Response Actions
- **Containment measures:** (Recommended) Revocation of all generated API keys and rotation of AWS IAM credentials.
- **Eradication steps:** (Recommended) Refactoring the API to use POST for state-changing actions and implementing strict CORS allow-listing.
- **Recovery actions:** (Recommended) Removal of plaintext passwords from EC2 metadata/tags.
## Lessons Learned
- **The "Sum of Parts" Risk:** Individually low-impact bugs (like a GET-based CSRF) can become critical when chained with others (CORS misconfiguration).
- **Insecure Defaults:** Using GET requests for state-changing operations violates REST principles and introduces CSRF risks.
- **Cloud Metadata Security:** Failure to restrict internal proxies allows for easy SSRF attacks against the AWS metadata service.
## Recommendations
- **Enforce Strict CORS:** Replace reflected origin logic with a strict allow-list of trusted domains.
- **Input Validation:** Implement rigorous URL filtering and validation on all proxy features to prevent access to internal IPs.
- **Secure Secret Management:** Never store passwords in plaintext within EC2 tags, metadata, or environment variables; use AWS Secrets Manager or KMS.
- **IMDSv2:** Mandate the use of Instance Metadata Service Version 2 (IMDSv2) to mitigate SSRF risks through session-oriented requests.