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PYSEC-2026-3465
No affected components available
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/
The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
- CVE-2026-53656Alias
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