Stealing AWS Credentials with a Redirect: A Cautionary Tale for Cloud Security

In the fast-moving world of cloud-native applications, Server-Side Request Forgery (SSRF) remains one of the most devastating vulnerabilities when left unaddressed. Particularly in environments like Amazon Web Services (AWS), an SSRF exploit can open the door to critical infrastructure compromise. Today, we examine a real-world attack scenario where an SSRF, combined with a clever redirection trick, led to the theft of AWS credentials — and how a single security best practice could have stopped it cold.

This blog is tailored for penetration testers seeking sharper skills and C-Suite executives responsible for strategic cyber risk management. We will delve into the attack chain, the business impact, preventative measures, and practical advice for leaders.

Understanding Server-Side Request Forgery (SSRF)

Server-Side Request Forgery occurs when an application fetches a remote resource based on user input — but fails to validate or sanitise the input correctly. As a result, attackers can craft malicious requests that the server executes internally.

Common targets include:

• Internal web applications
• Metadata services (like AWS IMDS)
• Redis instances, API servers, or cloud storage
• Sensitive system files (/etc/passwd)

In a cloud environment, metadata services are particularly attractive because they store temporary credentials that can provide access to other AWS services.

The Real-World Scenario: Moving App Vulnerability

During a penetration test of a home-moving service application hosted on AWS, our team identified a webhook feature that accepted arbitrary URLs.

Discovery:

• The application sent HTTP requests to user-supplied webhook URLs.
• There was no restriction on internal IP address ranges or hostnames.
• HTTP redirects (302 responses) were automatically followed.

Initially appearing benign, this behaviour created an opening for a chained attack — one where an attacker could carefully guide the server to fetch forbidden resources without directly pointing to them.

Breaking Down the Attack Chain

Here is a step-by-step breakdown of how the breach unfolded:

Step 1: Setting the Trap

• We hosted a malicious server that, upon receiving a request, immediately returned a 302 Redirect.
• The redirect pointed to http://169.254.169.254/latest/meta-data/, AWS’s Instance Metadata Service endpoint.

Step 2: Triggering the Server

• We submitted a crafted webhook URL pointing to our server.
• When the app executed the webhook request, it followed the 302 redirect to AWS’s metadata service.

Step 3: Capturing the Metadata

• The app fetched sensitive metadata, including temporary AWS credentials (Access Key ID, Secret Access Key, Session Token).
• Worse yet, the app logged the response internally, making it retrievable through the application interface.

Step 4: Escalating Privileges

• Using the stolen credentials, we enumerated:
  • IAM roles and permissions
  • S3 buckets
  • EC2 instances
  • Lambda functions
• In some configurations, privilege escalation might have been possible, including spinning up additional infrastructure or modifying application code.

The Role of AWS Instance Metadata Service (IMDS)

The Instance Metadata Service allows EC2 instances to retrieve configuration details, including temporary credentials for IAM roles.

AWS introduced IMDSv2 to mitigate SSRF attacks:

IMDSv2 requires a session-based token, making it significantly harder to exploit via SSRF — redirects or direct requests would fail without proper authentication.

Unfortunately, the target app in our case was running on IMDSv1, leaving it vulnerable.

The Business Impact: Why the C-Suite Should Care

To a CEO, CISO, or CFO, this scenario is not just a technical misconfiguration — it is a potential business catastrophe.

Here’s why:

A simple SSRF vulnerability can cascade into full environment compromise, leading to millions in damages — not to mention lasting brand damage.

Mitigation Strategies and Best Practices

1. Enforce IMDSv2

• Mandate IMDSv2 for all EC2 instances.
• Regularly audit configurations with AWS Config Rules.

2. Validate and Restrict Outbound Requests

• Only allow server requests to approved domains.
• Use a firewall or VPC endpoints to block unintended destinations.

3. Disable Automatic Redirects

• Prevent HTTP clients from following redirects automatically.
• Implement explicit allowlists for redirection targets.

4. Least Privilege IAM Roles

• Assign minimal permissions to EC2 roles.
• Continuously monitor for privilege creep.

5. Regular Penetration Testing

• Conduct thorough manual penetration tests, especially focused on cloud-specific attack chains.
• Test beyond automated scanners.

Why Automated Scanners Alone Are Not Enough

While cloud security scanners are excellent at spotting misconfigurations like IMDSv1, they rarely replicate complex, real-world attack chains like the redirect-based SSRF exploit.

Automated tools might:

• Flag open metadata access (sometimes).
• Miss chained redirects and log exposures.

Human creativity and attacker mindset are irreplaceable in cybersecurity.

Proactive, manual testing uncovers risks automation misses.

For C-Suite leaders, this underlines the importance of budgeting for manual pentesting alongside automated scanning and monitoring.

A Single Layer of Defence is Never Enough

The attack chain we uncovered serves as a harsh reminder: security by design is critical.

One missing control (IMDSv2) coupled with an insecure development practice (unrestricted webhook URLs) created a direct path from a single external request to cloud-wide credential compromise.

Key Takeaways:

• Assume every server feature can be weaponised.
• Cloud-specific vulnerabilities require cloud-specific thinking.
• Investing in manual security testing is not optional — it is business-critical.

Visual Summary: The SSRF Attack Chain

User Input (Webhook URL)

      ↓

Malicious Server (302 Redirect)

      ↓

AWS Metadata Service (IMDSv1)

      ↓

Credentials Retrieved and Logged

      ↓

Attacker Uses Stolen Credentials

      ↓

Environment Compromise

If your organisation relies on cloud infrastructure, act now:

• Review your IMDS configurations.
• Audit applications handling external inputs.
• Schedule a penetration test that includes cloud-specific attack scenarios.

Cloud security is no longer just an IT concern — it is a boardroom priority.

Executive Summary Checklist:

Preventing AWS Credential Theft via SSRF and Redirect Attacks

A one-page action guide for CEOs, CISOs, CTOs, and CFOs to proactively mitigate cloud risks.

🔒 Governance and Policy

• [ ] Mandate IMDSv2 for all AWS EC2 instances.
• [ ] Implement strict security policies for outbound server requests.
• [ ] Establish a URL allowlist for all webhook or external HTTP requests.
• [ ] Regularly audit cloud configurations using AWS Config or similar tools.

🔍 Risk Assessment and Penetration Testing

• [ ] Schedule annual manual penetration tests specifically targeting cloud attack chains (beyond automated scans).
• [ ] Include redirect-based SSRF scenarios in security assessments.
• [ ] Review logging mechanisms — ensure sensitive information like metadata responses is never logged.

🛡️ Cloud Infrastructure Hardening

• [ ] Configure firewall rules or VPC endpoints to block traffic to 169.254.169.254 (AWS metadata IP) unless explicitly allowed.
• [ ] Disable automatic HTTP redirects in server-side HTTP client libraries.
• [ ] Harden IAM roles:
  • Ensure Least Privilege Access is enforced.
  • Rotate credentials regularly.
  • Monitor roles with unusually broad permissions.

🧠 Awareness and Training

• [ ] Educate development teams on the risks of SSRF vulnerabilities.
• [ ] Train incident response teams to detect unusual credential usage or metadata service access attempts.
• [ ] Promote a ‘Secure by Design’ culture throughout product and engineering teams.

📊 Monitoring and Detection

• [ ] Implement real-time anomaly detection for AWS API usage.
• [ ] Monitor server logs for unexpected metadata service access patterns.
• [ ] Set up alerts for high-risk activities involving IAM role assumptions or privilege escalations.

🚀 Final Leadership Insights

✅ Cloud security must be layered and proactive.

✅ Relying solely on automated scanners creates blind spots.

✅ Manual pentests, infrastructure hardening, and continuous governance are essential to protect AWS assets and business continuity.

CISO Talking Points:

Stealing AWS Credentials via Redirected SSRF — Key Risks and Strategic Actions

1. What Happened

• During a security assessment, a Server-Side Request Forgery (SSRF) was exploited in a cloud-hosted app.
• The app followed a 302 redirect to AWS’s metadata service (169.254.169.254) exposing temporary AWS credentials.
• Using these credentials, attackers could enumerate permissions, access sensitive data, and pivot deeper into the cloud environment.

2. Why It Matters to the Business

3. Root Causes

• Failure to enforce IMDSv2 (AWS metadata service v2).
• Inadequate validation of external webhook URLs.
• Automatic following of HTTP redirects by server components.
• Over-permissive IAM roles.

4. Immediate Actions Recommended

✅ Mandate IMDSv2 on all EC2 instances.

✅ Implement strict allowlisting for outbound server requests.

✅ Block traffic to metadata IP ranges unless explicitly necessary.

✅ Disable automatic HTTP redirect following on server-side HTTP clients.

✅ Enforce Least Privilege on IAM roles and rotate temporary credentials frequently.

✅ Schedule manual cloud penetration testing, focusing on chained attack paths.

5. Strategic Priorities for the Next 90 Days

6. Key Leadership Message

“Cloud misconfigurations are now a leading cause of breaches. A small oversight, like leaving IMDSv1 active, can escalate to full cloud compromise. Proactive security hardening and rigorous manual testing are no longer optional — they are core to protecting business continuity and shareholder value.”

🎯 Final CISO Insights:

Secure the cloud environment now, before adversaries find the gaps.