Summary
Shiny for Python has path traversal in bookmark restore
Affected versions
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.
Workarounds
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.
Credits
Reported by @0xRenSec.
Impact
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 usingui.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.
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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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".
Frequently Asked Questions
- What is CVE-2026-108258? CVE-2026-108258 is a medium-severity path traversal vulnerability in shiny (pip), affecting versions >= 1.4.0, <= 1.6.3. It is fixed in 1.6.4. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- Which versions of shiny are affected by CVE-2026-108258? shiny (pip) versions >= 1.4.0, <= 1.6.3 is affected.
- Is there a fix for CVE-2026-108258? Yes. CVE-2026-108258 is fixed in 1.6.4. Upgrade to this version or later.
- Is CVE-2026-108258 exploitable, and should I be worried? Whether CVE-2026-108258 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-108258 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-108258? Upgrade
shinyto 1.6.4 or later.