Smarty: Symlink path traversal out of trusted directories

NVD Description

When Smarty's Security policy is enabled, secure_dir (and the configured template/trusted directories) restrict which local files a template may read via {include} and {fetch}. The trust check in Security::_checkDir() resolved the requested path with Smarty::_realpath(), which normalizes the path as a string only and does not follow symbolic links. A symlink placed inside a trusted directory therefore passed the trust check, while the underlying file_get_contents() followed it to an arbitrary file outside the sandbox (e.g. /etc/passwd). ## Impact An attacker able to (a) cause a symlink to exist inside a trusted directory (e.g. a user-upload area located within the template path) and (b) cause a template to reference that path can read arbitrary files readable by the PHP process, escaping the secure_dir boundary. Confidentiality impact only. ## Patches Fixed in 5.8.2. Security::_checkDir() now resolves the requested file with native realpath() and re-validates the canonical, symlink-free path against the trusted directories (which are canonicalized the same way, so legitimate symlinked deployment paths such as a Capistrano current symlink or macOS /var → /private/var keep working). It falls back to string normalization only when the file does not yet exist on disk. ## Workarounds Ensure no untrusted symlinks can be created within any directory listed in secure_dir/the trusted template directories; restrict write access to those directories to trusted processes only. ## References - Fix commit: 99c048c - CWE-22

Affected Packages (1)