{"id":"GHSA-mxmp-wr3w-rvqx","summary":"Fleet: IP spoofing allows bypassing API rate limiting","details":"### Summary\nA vulnerability in Fleet's IP extraction logic allows unauthenticated attackers to bypass API rate limiting by spoofing client IP headers. This may allow brute-force login attempts or other abuse against Fleet instances exposed to the public internet.\n\n### Impact\nFleet extracted client IP addresses from request headers (`True-Client-IP`, `X-Real-IP`, `X-Forwarded-For`) without validating that those headers originate from a trusted proxy. The extracted IP is used as the key for rate limiting and IP ban decisions.\n\nAs a result, an attacker could rotate the value of these headers on each request, causing Fleet to treat each attempt as coming from a different client. This effectively bypasses per-IP rate limits on sensitive endpoints such as the login API, enabling unrestricted brute-force or credential stuffing attacks.\n\nThis issue primarily affects Fleet instances that are directly exposed to the internet without a reverse proxy that overwrites forwarded-IP headers. Instances behind a properly configured proxy or WAF are less affected.\n\n### Workarounds\nIf an immediate upgrade is not possible, administrators should ensure Fleet is deployed behind a reverse proxy (e.g., nginx, Cloudflare, AWS ALB) that overwrites `X-Forwarded-For` with the true client IP, and apply rate limiting at the proxy or WAF layer.\n\n### For more information\nIf you have any questions or comments about this advisory:\nEmail us at [security@fleetdm.com](mailto:security@fleetdm.com)\nJoin #fleet in [osquery Slack](https://join.slack.com/t/osquery/shared_invite/zt-h29zm0gk-s2DBtGUTW4CFel0f0IjTEw)\n\n### Credits\nWe thank @fuzzztf for responsibly reporting this issue.","aliases":["CVE-2026-46356","GO-2026-5520"],"modified":"2026-06-25T23:11:35.533853619Z","published":"2026-05-14T13:18:33Z","database_specific":{"nvd_published_at":"2026-05-14T20:17:09Z","cwe_ids":["CWE-290"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-05-14T13:18:33Z"},"references":[{"type":"WEB","url":"https://github.com/fleetdm/fleet/security/advisories/GHSA-mxmp-wr3w-rvqx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-46356"},{"type":"PACKAGE","url":"https://github.com/fleetdm/fleet"},{"type":"WEB","url":"https://github.com/fleetdm/fleet/releases/tag/fleet-v4.80.1"}],"affected":[{"package":{"name":"github.com/fleetdm/fleet/v4","ecosystem":"Go","purl":"pkg:golang/github.com/fleetdm/fleet/v4"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.80.1"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-mxmp-wr3w-rvqx/GHSA-mxmp-wr3w-rvqx.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"}]}