CWE-552 Files Accessible to External Parties

Description

Files Accessible to External Parties

Reference: https://cwe.mitre.org/data/definitions/552.html

OWASP Category: A01:2021 – Broken Access Control

---

Vulnerable Pattern

❌ Example 1: Vulnerable Pattern

// VULNERABLE: Serving files without access control
@GetMapping("/files/{filename}")
public ResponseEntity<Resource> getFile(@PathVariable String filename) {
    Path path = Paths.get("/uploads/" + filename);
    Resource resource = new FileSystemResource(path);
    return ResponseEntity.ok().body(resource);
}

Why it's vulnerable: This pattern is vulnerable to Files Accessible to External Parties

---

Deterministic Fix

✅ Secure Implementation: Secure Implementation

// SECURE: Validate access and sanitize filename
@GetMapping("/files/{filename}")
public ResponseEntity<Resource> getFile(@PathVariable String filename, Authentication auth) {
    // Sanitize filename
    String safeName = Paths.get(filename).getFileName().toString();
    // Verify user has access
    FileMetadata meta = fileService.getMetadata(safeName);
    if (!meta.canAccess(auth.getName())) {
        throw new AccessDeniedException("Access denied");
    }
    Path path = uploadDir.resolve(safeName);
    return ResponseEntity.ok().body(new FileSystemResource(path));
}

Why it's secure: Implements proper protection against Files Accessible to External Parties

---

Detection Pattern

Look for these patterns in your codebase:

# Find file serving endpoints
grep -rn "FileSystemResource\\|getFile\\|download" --include="*Controller.java"

---

Remediation Steps

1. Validate user authorization before serving files

2. Sanitize filenames to prevent path traversal

3. Store files outside web root

4. Implement access control lists for files

---

Key Imports

import org.springframework.core.io.FileSystemResource;

import java.nio.file.Paths;

---

Verification

After remediation:

• Run SAST scanner to confirm vulnerability is resolved

• Review all instances of the vulnerable pattern

• Add unit tests that verify the secure implementation

• Check for similar patterns in related code

---

Trigger Examples

Fix CWE-552 vulnerability
Resolve Files Accessible to External Parties issue
Secure this Java code against files accessible to external parties
SAST reports CWE-552

---

Common Vulnerable Locations

| Layer | Files | Patterns | |-------|-------|----------|

| Controller | *Controller.java | User input handling |

| Service | *Service.java | Business logic |

| Repository | *Repository.java | Data access |

---

References

• CWE-552: Files Accessible Externally

---

Source: Generated by Java CWE Security Skills Generator Last Updated: 2026-03-07