Summary
FiftyOne App server uses wildcard CORS (Access-Control-Allow-Origin: *), enabling cross-origin reads of local server data
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/
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.
CVE-2026-53656 has a CVSS score of 6.3 (Medium). The vector is requires local access, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.17.0); upgrading removes the vulnerable code path.
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 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.
Frequently Asked Questions
- What is CVE-2026-53656? CVE-2026-53656 is a medium-severity security vulnerability in fiftyone (pip), affecting versions < 1.17.0. It is fixed in 1.17.0.
- How severe is CVE-2026-53656? CVE-2026-53656 has a CVSS score of 6.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of fiftyone are affected by CVE-2026-53656? fiftyone (pip) versions < 1.17.0 is affected.
- Is there a fix for CVE-2026-53656? Yes. CVE-2026-53656 is fixed in 1.17.0. Upgrade to this version or later.
- Is CVE-2026-53656 exploitable, and should I be worried? Whether CVE-2026-53656 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-2026-53656 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-2026-53656? Upgrade
fiftyoneto 1.17.0 or later.