How severe is CVE-2026-108258?

No CVSS score has been assigned to CVE-2026-108258 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-108258?

CVE-2026-108258 affects the following packages: shiny (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-108258?

Update shiny to 1.6.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-108258 is resolved across your whole dependency graph.

How do I detect CVE-2026-108258 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for shiny, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-108258 if there is no patch (or I can't update yet)?

Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Is CVE-2026-108258 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-108258 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-108258?

CVE-2026-108258 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 28th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-108258?

CVE-2026-108258 is classified as Path Traversal (CWE-22). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-108258 published, and has it been updated?

CVE-2026-108258 was published on October 9, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-108258 — shiny

Fix: posit-dev/py-shiny@1d8ecb4

CVE-2026-108258 is a Path Traversal vulnerability in shiny. A fix is available for shiny — see the affected versions and patch details below.

Shiny for Python - Path traversal in bookmark restore

Also known asGHSA-47c3-hpmg-7j6pPYSEC-2026-4300

Published

Oct 9, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-108258.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs28th percentile — riskier than 28% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍shiny

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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 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.

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.

Patches

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".

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`shiny`	≥ 1.4.0&&< 1.6.4	1.6.4`pip install --upgrade 'shiny==1.6.4'`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for shiny, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update shiny to 1.6.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-108258 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Frequently Asked Questions

### 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 configu

O3 Security · Impact-Aware SCA

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