PYSEC-2026-1967

## Description A critical path traversal vulnerability (CWE-22) has been identified in the `review_paper` function in `backend/app.py`. The vulnerability allows malicious users to access arbitrary PDF files on the server by providing crafted file paths that bypass the intended security restrictions.

## Impact This vulnerability allows attackers to: - Read any PDF file accessible to the server process - Potentially access sensitive documents outside the intended directory - Perform reconnaissance on the server's file system structure

## Vulnerable Code The issue occurs in the `review_paper` function around line 744:

```python if pdf_path.startswith("/api/files/"): # Safe path handling for API routes relative_path = pdf_path[len("/api/files/"):] generated_base = os.path.join(project_root, "generated") absolute_pdf_path = os.path.join(generated_base, relative_path) else: absolute_pdf_path = pdf_path # VULNERABLE: Direct use of user input ```

## Proof of Concept ```bash curl -X POST http://localhost:5000/api/review \ -H "Content-Type: application/json" \ -d '{"pdf_path": "/etc/passwd"}' ```

## Credit This vulnerability was discovered and reported by Ruizhe.