Symlink Attack Affecting tornado package, versions [,6.5.9)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-TORNADO-20415627
- published3 Oct 2026
- disclosed1 Oct 2026
- creditUnknown
Introduced: 1 Oct 2026
NewCVE-2026-103263 (opens in a new tab)How to fix?
Upgrade tornado to version 6.5.9 or higher.
Overview
tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed.
Affected versions of this package are vulnerable to Symlink Attack via StaticFileHandler.validate_absolute_path in tornado/web.py, which uses os.path.abspath to validate that a requested path remains within the configured static root directory but does not resolve symlinks. An attacker can place or exploit a symlink inside the static directory that points to an arbitrary location on the filesystem, causing StaticFileHandler to serve files outside the intended root - both symlinked files and symlinked directories are affected. The fix introduces a secondary check using os.path.realpath against a configurable allowed_symlink_directory boundary.
Note: This is only exploitable when a symlink exists inside the configured static directory pointing to a location outside it.