T05 · Unauthorized Access and Privilege Escalation
Error
- Location
- references/dynamic-dns.md:165
- Finding
- Unauthenticated webhook permits arbitrary DNS modification and path traversal<![CDATA[ ## Vulnerability Details **File Location**: `references/dynamic-dns.md:165-197` **Vulnerability Type**: Missing authentication, missing authorization, path traversal, and unsafe automatic DNS deployment **Risk Level**: Critical ### Vulnerable Code ```python @app.route('/update', methods=['POST']) def update_dns(): data = request.json # Update zone file zone_file = f"config/{data['zone']}.yaml" with open(zone_file, 'r') as f: zone = yaml.safe_load(f) zone[data['name']] = { 'type': data['type'], 'value': data['value'], 'ttl': data.get('ttl', 300) } with open(zone_file, 'w') as f: yaml.dump(zone, f) # Sync result = subprocess.run([ 'scripts/sync.sh', '--zone', data['zone'], '--doit' ], capture_output=True, text=True) return { 'success': result.returncode == 0, 'output': result.stdout } if __name__ == '__main__': app.run(port=5000) ``` ### Technical Analysis The documented webhook accepts arbitrary JSON and performs a privileged DNS update without authenticating or authorizing the caller. There is no zone allowlist, request signature, API token, replay protection, or validation of record names, types, values, and TTLs. The attacker-controlled `zone` is also inserted directly into a filesystem path: ```python zone_file = f"config/{data['zone']}.yaml" ``` Values such as `../target` can escape the intended `config` directory and address another YAML file available to the process. After modifying the file, the handler invokes `sync.sh` with `--doit`, immediately applying the change rather than performing a preview or requiring approval. Although Flask binds to loopback by default in this exact example, any local process can call it, and a deployment that exposes or proxies the service would make the vulnerability remotely reachable. ### Attack Path 1. The operator implements and starts the ...[truncated 934 chars]
- Remediation
- <![CDATA[ ## Remediation Suggestions - Require authenticated requests using a strong API token, mutual TLS, or signed requests. - Authorize each identity against an explicit zone and operation allowlist. - Bind to loopback explicitly unless remote access is required; if exposed, place the service behind authenticated TLS. - Parse and validate the request against a strict schema. - Allowlist supported DNS record types and validate values according to their record type. - Restrict TTLs to an approved range. - Resolve the requested file with `pathlib.Path.resolve()` and verify that it remains beneath the intended configuration directory. - Reject zone values containing separators, traversal components, control characters, or invalid DNS syntax. - Run a dry-run first and require approval for the exact generated plan before executing `--doit`. - Use narrowly scoped DNS credentials and keep an immutable audit log of the caller, requested change, preview, approval, and provider response. ]]>