Affected: Homebrew: livereload

### Summary StaticFileHandler allows an unauthenticated attacker to read arbitrary files from the server's filesystem by requesting a path that resolves to a symbolic link placed inside the static root directory. Any application that serves user-uploadable content, or whose static directory is populated by a build/deploy pipeline that creates symlinks (e.g. npm link, webpack, Docker volume mounts, CDN sync tools), is affected. An attacker who can trigger the creation of a symlink pointing outside the static root—or exploit one that already exists—can retrieve sensitive files such as /etc/passwd, private keys, configuration files, or application secrets.

### Details The vulnerability is in tornado.web.StaticFileHandler, specifically in the interaction between two methods in [tornado/web.py](vscode-webview://1grdaaa6v64itrol06qu70pq3d1b9h9im5c3npvvc9snaprc1q9f/tornado/web.py): - [get_absolute_path](https://github.com/tornadoweb/tornado/blob/0ca3c5f8279d402b245718d16522bc18a8f5d958/tornado/web.py#L2932) uses `os.path.abspath()` to resolve the requested path: - [validate_absolute_path](https://github.com/tornadoweb/tornado/blob/0ca3c5f8279d402b245718d16522bc18a8f5d958/tornado/web.py#L2935) uses the same `os.path.abspath()` on the root, then performs a string prefix check:

`os.path.abspath()` normalises . and .. segments but does not resolve symbolic links. As a result, a path like `/var/www/static/link` passes the `startswith("/var/www/static/")` check regardless of where `l…

Tornado before 6.5.9 contains a path traversal vulnerability in StaticFileHandler that follows symbolic links inside the static root without confirming the resolved target stays within it. When a symlink pointing outside the static directory exists inside it, unauthenticated attackers can request it to read files such as configuration files, private keys, and application secrets accessible to the process user.

Tornado before 6.5.9 contains a path traversal vulnerability in StaticFileHandler that follows symbolic links inside the static root without confirming the resolved target stays within it. When a symlink pointing outside the static directory exists inside it, unauthenticated attackers can request it to read files such as configuration files, private keys, and application secrets accessible to the process user.

Affected: Ubuntu:Pro:16.04:LTS: python-tornado, Ubuntu:Pro:18.04:LTS: python-tornado, Ubuntu:Pro:20.04:LTS: python-tornado, Ubuntu:Pro:22.04:LTS: python-tornado, Ubuntu:24.04:LTS: python-tornado, Ubuntu:26.04:LTS: python-tornado

Tornado before 6.5.9 contains a path traversal vulnerability in StaticFileHandler that follows symbolic links inside the static root without confirming the resolved target stays within it. When a symlink pointing outside the static directory exists inside it, unauthenticated attackers can request it to read files such as configuration files, private keys, and application secrets accessible to the process user.