CWE-61 — Vulnerability Class 100

CWE-61 represents a critical input validation weakness where software fails to adequately verify the final destination of a symbolic link during file or directory access operations. Attackers typically exploit this vulnerability by crafting malicious symlinks that point to sensitive system files or directories outside the application’s intended control sphere. When the vulnerable program follows these links, it inadvertently reads, modifies, or deletes unauthorized data, potentially leading to information disclosure, privilege escalation, or denial of service. To mitigate this risk, developers must implement strict path canonicalization and validation mechanisms before processing any file paths. This involves resolving symbolic links to their absolute physical paths and ensuring the resulting target resides within an allowed directory tree. Additionally, using secure file handling APIs that explicitly reject symlink traversal or employing chroot jails can effectively isolate applications from such path manipulation attacks.