From a Stack Trace to SAP Takeover: How a Simple Error Message Can Lead to Full Portal Compromise + Video

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Introduction:

A single stack trace—often dismissed as a harmless debugging artifact—can be the starting point for a devastating cyberattack. When web applications or SAP portals expose verbose error messages, they inadvertently leak internal paths, database queries, and even credentials. This article dissects how threat actors pivot from a simple stack trace to gaining unauthorized access to an SAP portal, using real-world techniques and tools. We’ll explore the technical steps, from reconnaissance to exploitation, and provide actionable defenses.

Learning Objectives:

  • Understand how stack trace information disclosure can compromise SAP systems.
  • Learn to identify, extract, and exploit sensitive data from stack traces.
  • Implement robust error handling and SAP security configurations to mitigate such risks.

You Should Know:

1. Understanding Stack Trace Leakage in Web Applications

Stack traces are generated when an application encounters an unhandled exception. In production environments, they should never be displayed to end users. However, misconfigured servers often expose them, revealing:
– Full file system paths
– Database query structures
– Library versions and internal IP addresses
– Occasionally, hardcoded credentials or API keys

Step‑by‑Step Guide to Detecting Stack Traces:

  • Using Browser Developer Tools: Open the Network tab, trigger an error (e.g., by submitting malformed input), and inspect the response body for stack traces.
  • Using Burp Suite: Intercept requests and intentionally cause errors (e.g., SQL injection payloads) to see if the application returns a stack trace in the response.
  • Automated Scanning with curl: 
    curl -X POST https://target.com/sap/public/bc/ur/some-endpoint -d "malformed=payload" -v

    Look for phrases like at com.sap., java.lang., or `Stack Trace:` in the output.

  1. Reconnaissance: Extracting SAP System Information from Stack Traces
    Once a stack trace is discovered, the next step is to extract actionable intelligence. SAP systems often reveal internal URLs, function module names, and database table names.

Commands to Extract SAP-Specific Data:

  • Grep for SAP Keywords: 
    curl -s https://target.com/sap/bc/soap/rfc | grep -iE 'sap|rfc|bapi|jco'
  • Enumerate SAP RFC Functions: Use a tool like `sapyto` or manually craft SOAP requests. Example SOAP request to list RFC functions: 
    <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<RfcFunction>
<functionName>RFC_FUNCTION_SEARCH</functionName>
</RfcFunction>
</soap:Body>
</soap:Envelope>

    Send it via curl and analyze the error response for stack traces that might reveal available functions.

  1. Exploiting Stack Traces to Enumerate Hidden SAP Endpoints
    Stack traces often include absolute file paths that can be used to discover undocumented endpoints. For instance, a path like `/usr/sap/trans/tmp/` might hint at a file upload endpoint.

Fuzzing for Hidden SAP URLs with ffuf:

ffuf -u https://target.com/FUZZ -w /usr/share/wordlists/dirb/common.txt -fc 404 -t 50

Combine this with paths gleaned from stack traces (e.g., /sap/bc/soap/, /sap/public/).

  1. Leveraging Stack Trace Details for Authentication Bypass
    Stack traces may inadvertently expose SQL queries that reveal table names or even credentials. If a query like `SELECT FROM users WHERE username = ‘admin’ AND password = ‘…’` appears, you can attempt SQL injection.

Example SQLMap Command Targeting a Susceptible Parameter:

sqlmap -u "https://target.com/sap/bc/soap/rfc?param=1" --data="soap=..." --dbms=oracle --dump

Alternatively, if the stack trace shows a default SAP login endpoint (e.g., /sap/bc/gui/sap/its/webgui), try default credentials:
– `SAP/PASS`
– `DDIC/19920706`

5. Gaining Access to SAP Portal

Once inside, privilege escalation is often possible through misconfigured SAP roles or known vulnerabilities. A common vector is exploiting the SAP RECON vulnerability (CVE-2020-6287), which allows unauthenticated attackers to create new users with administrative privileges.

Steps to Exploit CVE-2020-6287 (if applicable):

  1. Identify an SAP NetWeaver system with the vulnerable component.
  2. Send a crafted request to create a new user: 
    POST /sap/bc/webdynpro/sap/xyz/?sap-client=100 HTTP/1.1
Host: target.com
Content-Type: application/x-www-form-urlencoded</li>
</ol>

... (payload to add user)

    3. Use the newly created account to access SAP GUI or web interfaces.

    1. Mitigation: Secure Error Handling and SAP Hardening
      To prevent stack trace leakage, implement the following configurations:

    For Apache/nginx Web Servers:

    • Custom error pages: 
      ErrorDocument 500 /error_pages/500.html
    • Disable display of PHP errors: 
      display_errors = Off
log_errors = On

    For SAP Application Servers:

    • In transaction RZ10, set parameter `icm/HTTP/error_handling` to `2` (hide internal errors).
    • Disable detailed error messages in SAP Web Dispatcher by setting icm/HTTP/logging_errors = 0.
      1. Automated Detection of Stack Trace Leaks Using AI/ML
        Machine learning models can be trained to detect sensitive data in HTTP responses or logs. For example, using TensorFlow or scikit-learn, you can build a classifier that flags responses containing stack traces.

    Example Using Python and Regex (Simple Rule-Based Detection):

    import re
import requests

response = requests.get("https://target.com/sap/bc/soap/rfc")
if re.search(r"(Exception|Stack trace|at java.|at com.sap.)", response.text):
print("Potential stack trace leak detected!")

    AI can enhance this by learning new patterns from large datasets, reducing false positives.

    What Undercode Say:

    • Key Takeaway 1: Stack traces are a critical information leak—they expose system internals and can be the first step in a chain leading to full SAP compromise. Always sanitize error messages in production.
    • Key Takeaway 2: SAP environments are particularly susceptible due to their complexity and legacy configurations. Regular penetration testing and adherence to SAP security notes are non-negotiable.
    • Analysis: The attack vector described underscores the need for secure coding practices and continuous monitoring. While stack traces may seem trivial, they often reveal the “blueprint” of an application. Organizations must invest in both technology (e.g., Web Application Firewalls) and training (like the 57 certifications held by experts such as Tony Moukbel) to stay ahead of threat actors.

    Prediction:

    As SAP systems increasingly migrate to the cloud, we will witness a surge in automated bots scanning for stack trace leaks. Attackers will combine traditional reconnaissance with AI to rapidly exploit these vulnerabilities. Conversely, defenders will deploy AI-driven anomaly detection to identify and block such reconnaissance in real time. The arms race between exploitation and mitigation will intensify, making continuous education and adaptive security measures essential.

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