Shiny for Python's bookmark-restore path accepted a client-supplied _state_id_
query-string value and joined it into the server-side bookmark directory
(<cwd>/shiny_bookmarks/<id>) without validating it. A value containing ..
path segments, or an absolute path, could therefore cause the server to open and
parse input.json and values.json from a directory outside the bookmark store.
On a default application the restore was attempted whenever the client supplied a
URL query string — including when bookmarking was disabled
(bookmark_store="disable") — so no opt-in configuration was required. For such
applications the impact is an unauthenticated, server-side probe for the
existence and JSON-validity of attacker-chosen paths, constrained to those two
file names.
Applications configured with bookmark_store="server" and using
ui.input_file() are affected more seriously. The file-input restore handler
copies files out of the restore directory, so the contents of an
attacker-selected file name within an attacker-selected directory could be read
into the application.
1.4.0 through 1.6.3. Bookmarking was introduced in 1.4.0; earlier releases do not contain the affected code path and are not affected.
Fixed in 1.6.4. Upgrade with:
pip install --upgrade shiny
The fix validates bookmark IDs against an allowlist — a single path segment
matching [A-Za-z0-9_-]+, which cannot express a path separator, a .. parent
reference, or an absolute path — before the ID is used to build a filesystem
path. Bookmark IDs generated by Shiny are unaffected by this restriction.
Restore is additionally gated on the application's bookmark_store setting at a
single point, so it no longer runs when bookmarking is disabled, and the on-disk
restore path is honored only under bookmark_store="server".
There is no configuration change that mitigates this on an affected version:
the restore path ran even with bookmark_store="disable". Deployments that
cannot upgrade immediately can strip the _state_id_ parameter from incoming
query strings at a reverse proxy or load balancer, which prevents the affected
code path from being reached.
Reported by @0xRenSec.
{
"cwe_ids": [
"CWE-22"
],
"github_reviewed": true,
"github_reviewed_at": "2026-10-09T20:56:37Z",
"nvd_published_at": null,
"severity": "MODERATE"
}