CVE-2025-27553: Path Traversal in Apache Commons VFS

The vulnerability lies within the resolveFile method of the FileObject API in Apache Commons VFS. When the 'scope' parameter is set to 'NameScope.DESCENDENT', the method is intended to throw an exception if the resolved file is not a descendant of the base file. However, by crafting malicious paths containing encoded ".." sequences (e.g., "%2E%2E/bar.txt"), an attacker can bypass this check and potentially access files outside the intended directory structure. This could expose sensitive configuration files, source code, or other critical data. The blast radius extends to any application utilizing Apache Commons VFS to handle file operations, potentially impacting multiple services and users.

1. Reserved2025-03-01
2. Published2025-03-23
3. Modified2025-04-03
4. EPSS updated2026-03-23

The primary mitigation for CVE-2025-27553 is to upgrade to Apache Commons VFS version 2.10.0 or later, which addresses the vulnerability. If immediate upgrading is not feasible, consider implementing temporary workarounds. One approach is to sanitize user-provided file paths, removing or encoding potentially malicious characters like ".." and "%2E%2E". Web Application Firewalls (WAFs) can be configured to block requests containing suspicious path patterns. Additionally, review and restrict file access permissions to minimize the potential impact of a successful exploit. After upgrading, verify the fix by attempting to access files outside the intended directory structure using crafted paths containing encoded ".." sequences; the access should be denied.