CVE-2026-53656 is a medium-severity (CVSS 6.3) CWE-346 vulnerability in fiftyone. A fix is available for fiftyone — see the affected versions and patch details below.
FiftyOne App server uses wildcard CORS (Access-Control-Allow-Origin: *), enabling cross-origin reads of local server data
Exploitation Status
No confirmed exploitation observed yet
- 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-2026-53656.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-53656 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
fiftyoneReal-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
The FiftyOne App/API server (fiftyone/server/app.py) and the /media route (fiftyone/server/routes/media.py) unconditionally set a permissive CORS header (Access-Control-Allow-Origin: *) on their responses. Because the embedded App server runs locally and is unauthenticated, this allows any website a user visits to make cross-origin requests to that user's running FiftyOne server and read the responses.
Combined with the unauthenticated /media endpoint — which serves files from the local filesystem by path — the wildcard CORS policy turns a local-only file read into a remotely exploitable, drive-by data exfiltration vulnerability. A malicious web page can silently issue requests such as http://localhost:5151/media?filepath=/etc/passwd and read arbitrary files accessible to the server process (SSH keys, cloud credentials, .env files, dataset media, etc.), then exfiltrate them to an attacker-controlled endpoint.
The victim only needs to have a FiftyOne server running locally and visit a malicious page — no clicks or other interaction are required. Browsers that have shipped Private Network Access / local-network-access protections (e.g. Chromium 142+) mitigate this for some users, but Safari and Firefox do not yet, so the attack remains viable in common configurations.
Who is impacted: any user running FiftyOne (the open-source, embedded App server) locally while also browsing the web.
Not affected: media stored in cloud buckets, which is served via signed URLs on a separate origin.
Patches
Fixed in FiftyOne 1.17.0. The hard-coded Access-Control-Allow-Origin: * has been removed and the server now responds same-origin only by default, which covers local desktop usage and the supported notebook integrations (each served through a same-origin proxy or iframe).
Cross-origin access is now opt-in via a new allowed_origins config option (environment variable FIFTYONE_ALLOWED_ORIGINS), an explicit comma-separated list of trusted origins, e.g.:
export FIFTYONE_ALLOWED_ORIGINS='https://app.example.com,http://localhost:3000'
The literal value * restores the legacy wildcard behavior for users who explicitly require it and emits a warning.
Users should upgrade to FiftyOne 1.17.0 or later.
Workarounds
In affected versions there is no configuration flag to disable the wildcard CORS header without upgrading. Until you can upgrade:
- Do not run the FiftyOne App server while browsing untrusted websites.
- Keep the App server bound to
localhost(the default) and avoid exposing it on a network interface. - Use a browser that enforces Private Network Access protections.
Resources
- OWASP A01:2025 – Broken Access Control: https://owasp.org/Top10/2025/A01_2025-Broken_Access_Control/
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | fiftyone | all versions | 1.17.0pip install --upgrade 'fiftyone==1.17.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fiftyone, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update fiftyone to 1.17.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53656 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2026-53656 in your dependencies?
Find it across PyPI, including transitive dependencies.