CWL Cloud Breaker - SSRF to EC2 Role Impact

Executive summary (short & tasty): I hacked a cloud service where a vulnerable EC2-hosted web app with a server-side fetch feature exposed the instance metadata surface via SSRF, allowing temporary IAM role credentials to be disclosed. The chain illustrates how a tiny input-validation slip can become a catastrophic cloud identity compromise.

This document covers: reconnaissance, enumeration, exploitation characterization (redacted), credential validation (redacted), pivot scenarios (conceptual), detection opportunities, remediation playbook, and a prioritized hardening checklist. All live identifiers are replaced with REDACTED_* tokens.

Lab Context & Safety Posture

Environment: Isolated lab account / sandbox provided by CyberWarFare Labs
Scope: Single EC2 instance + attached IAM role; no production systems touched
Controls: Logging enabled, ephemeral resources, pre-agreed rollback plan
Redaction policy: All IPs, account IDs, role names, secret material and precise metadata addresses replaced with REDACTED_*

1) Reconnaissance — S3, Wayback, GitHub
2) Discovery — IP scanning, header fingerprinting
3) Application analysis — forms, params, behaviors
4) SSRF characterization — safe validation approach
5) Credential extraction — redacted artifact description
6) Post-exploitation verification
7) Blast radius & pivot strategies
8) Detection playbook
9) Remediation & hardening
10) Tactical defensive templates
11) Lab replication guidance
12) Incident response checklist
13) Timeline & artifact catalog
14) Lessons learned

1) Reconnaissance — Starting with Low-Hanging Fruit

Goals: find public storage, historical artifacts, and repo leakage that point to endpoints or keys.

Actions (redacted / conceptual):

S3-style probing of common bucket naming patterns: results returned HTTP_STATUS_NOT_FOUND for the tested names
Attempted Wayback/archival harvesting — tooling absent in the specific lab VM; method noted for future runs
GitHub OSINT: discovered https://github.com/REDACTED_ORG/REDACTED_REPO containing cloud service account artifacts — for a different provider (non-AWS)

Notes & Analysis: Multi-cloud leakage is a real foot-gun; finding keys for a different cloud often indicates engineering hygiene issues and could enable lateral pivot in cross-cloud setups. No public buckets were found for standard name patterns, so we pivoted to host discovery.

2) Discovery — Find the Running Asset (IP-based)

Method: iterate lab subnet, perform HTTP/host checks (non-destructive), and fingerprint the web service headers.

Findings (redacted):

A host responded at REDACTED_IP with HTTP 200 and server signature resembling Apache/REDACTED_VER (Ubuntu)
Additional headers indicated typical LAMP stack responses; webroot served a simple app UI

Verification of hosting provider (redacted): Whois/ASN lookup mapping confirmed the IP was allocated to REDACTED_CLOUD_PROVIDER. This validated an EC2-hosted hypothesis and focused the cloud pivot analysis.

3) Application Analysis — The Juicy Artifact: update.html + process.php

Observed assets (redacted):

http://REDACTED_IP/update.html — contained a form with fields: url, date, ip, organization
Form POSTs were handled by process.php (server-side script). App echoing/processing behavior suggested server-side retrieval of user-supplied ip/url content

Important observation: The ip parameter is likely used in a fetch routine (fetch, curl, file_get_contents(), etc.) — classic SSRF surface if not validated.

Safe testing approach used: Observed application responses to harmless, external test URLs to confirm retrieval behavior. No internal metadata queries were performed without proper authorizations (details redacted).

4) SSRF Characterization — How We Safely Tested for Server-Side Fetching

Threat model recap: If a process on the instance accepts a user-supplied URL and performs an outbound HTTP fetch, that process can be induced to retrieve internal-only endpoints (e.g., cloud metadata) — which exposes identity material.

Safe, redacted validation flow (conceptual):

Submit a lab-controlled external URL that returns a known marker
Confirm that marker appears in the application's response/logs — indicates server-side fetch capability
Once SSRF behavior is confirmed, escalate only within lab rules to verify internal reachability to internal-only endpoints

Result: SSRF behavior confirmed for ip parameter; application could fetch internal services reachable from the instance.

5) Credential Extraction — Artifact Description (Redacted)

What was observed (sanitized):

                        {
  "AccessKeyId": "REDACTED_KEY",
  "SecretAccessKey": "REDACTED_SECRET", 
  "Token": "REDACTED_SESSION_TOKEN",
  "Expiration": "REDACTED_EXPIRATION_TIMESTAMP"
}
                    

Important note: The credentials were temporary and associated with the EC2 instance role REDACTED_ROLE. No permanent long-lived credentials were discovered in this chain.

Security classification: High — exposure of temporary IAM credentials that map to an instance-attached role is a critical identity disclosure.

6) Post-Exploitation Verification — Conceptual Validation & Safe Checks

(Everything redacted and conceptual — performed in-lab only.)

Purpose of verification: ensure the extracted credentials are real and to enumerate what the role could access, so defenders can prioritize remediations.

Conceptual checks performed:

Use the extracted temporary credentials to call a get-caller-identity-equivalent (redacted) to verify principal identity and role assumption shape
Enumerate a minimal set of permitted APIs to determine blast radius (listing accessible buckets, reading permitted object metadata, etc.) — all within lab authorization

Outcome: credentials were valid and capable of performing actions allowed by the instance role.

7) Blast Radius & Pivot Scenarios (Conceptual — No Live Actions)

From the role's permissions, an adversary could conceptually:

Enumerate object stores and download objects if read permission exists
List compute resources and discover other instances or functions to attack
Create ephemeral compute (if allowed) to achieve persistence
Access secrets/parameter stores (if permitted) to obtain further credentials
Chain trust relationships by using permissive role policies (conceptual escalation)

Risk Matrix (Redacted Labels):

Vector	Ease (Low/Med/High)	Impact (Low/Med/High)
Read S3-like buckets	High	High
Assume cross-account role	Medium	High
Deploy serverless backdoor	Low	High
Exfiltrate DB snapshots	Medium	High

8) Detection Playbook — What Defenders Should Implement Now

Below are concrete detection ideas (safe to implement, non-actionable). Build these rules into your SIEM/IDS/WAF:

CloudTrail / Audit-based:

Alert: EventName == "GetCallerIdentity" originating from an instance principal that doesn't match deployment automation accounts → Critical
Alert: AssumeRole events where source is an instance principal and not a known automation identity → High

Network / Host-based:

Alert: Outbound HTTP(S) from web server process to internal-only CIDR or metadata address → Critical
Alert: Web processes performing high-frequency outbound fetches to many different hosts (abnormal for typical app behavior) → Medium

Application / WAF:

Rule: Block requests containing internal-only URL patterns or IP ranges in parameters that are used server-side for fetches
Rule: Rate-limit and challenge (CAPTCHA) for forms that accept external URLs

9) Prioritized Remediation & Hardening Playbook

Priority 1 — Immediate (minutes to hours):

Enforce metadata protection: require platform metadata service protections (session-based metadata requirement / IMDSv2 or equivalent)
Lock down instance IAM roles: change role policies to least privilege; remove broad * actions
Input allowlist: stop server-side fetches to arbitrary hosts — implement strict allowlists for any external fetcher feature

Priority 2 — Short term (hours to days):

Add WAF rules to detect and block SSRF-like input patterns
Rotate any exposed credentials and invalidate sessions (if applicable)
Improve logging to detect future similar attempts (host, app, cloud audit pipeline)

Priority 3 — Strategic (days to weeks):

CI/CD secret scanning: implement automated scanning for leaked secrets in repos and artifact stores
Network segmentation: limit egress from web tiers to required endpoints only
Threat modeling & least-privilege review across roles and policies

10) Tactical Defensive Templates (Redacted & Safe to Copy)

Example: Minimal IAM policy for instance role (CONCEPTUAL)

                        {
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "AllowReadOnlySpecificBucket",
      "Effect": "Allow",
      "Action": [
        "s3:GetObject",
        "s3:ListBucket"
      ],
      "Resource": [
        "arn:aws:s3:::REDACTED_BUCKET",
        "arn:aws:s3:::REDACTED_BUCKET/*"
      ]
    }
  ]
}
                    

WAF pseudo-rule (conceptual): If request body contains a parameter used for server fetch AND value resolves to internal-only hostnames/IPs or metadata-like patterns → block + alert.

12) Incident Response Checklist (Fast, Practical)

If you detect this in production (don't panic, act):

Isolate: limit the instance's network egress and isolate the workload
Rotate: revoke/rotate exposed credentials and force session invalidation
Audit: collect CloudTrail logs and host logs to build a timeline of requests by the compromised principal
Contain: enforce IMDS protections and deploy emergency WAF rule to block SSRF-like inputs
Eradicate: remove the vulnerable code path, patch the app, and redeploy with improved validation
Remediate: least-privilege review and rotation of roles/keys system-wide as needed
Review: run tabletop to update runbooks and detection rules

14) Lessons Learned — Another Way of Saying "Don't Be Sloppy"

SSRF is an identity problem in cloud contexts — input validation alone is not enough if the instance can reach identity endpoints
Make metadata access harder, not easier: IMDSv2-like protections + network egress controls
Logging + SIEM rules win investigations — detect the reconnaissance before the extraction
Developer hygiene matters: secrets in repos, test keys, and permissive IAM are consistent root causes

Shoutout: CyberWarFare Labs — thanks for the range practice.

All testing conducted in authorized lab environments with proper scope and controls.

CWL Cloud Breaker — SSRF → EC2 Role Impact