GHSA-MXMP-WR3W-RVQX
Vulnerability from github – Published: 2026-05-14 13:18 – Updated: 2026-05-15 23:45Summary
A 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.
Impact
Fleet 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.
As 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.
This 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.
Workarounds
If 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.
For more information
If you have any questions or comments about this advisory: Email us at security@fleetdm.com Join #fleet in osquery Slack
Credits
We thank @fuzzztf for responsibly reporting this issue.
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/fleetdm/fleet/v4"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "4.80.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-46356"
],
"database_specific": {
"cwe_ids": [
"CWE-290"
],
"github_reviewed": true,
"github_reviewed_at": "2026-05-14T13:18:33Z",
"nvd_published_at": "2026-05-14T20:17:09Z",
"severity": "MODERATE"
},
"details": "### Summary\nA vulnerability in Fleet\u0027s 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.",
"id": "GHSA-mxmp-wr3w-rvqx",
"modified": "2026-05-15T23:45:48Z",
"published": "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"
}
],
"schema_version": "1.4.0",
"severity": [
{
"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",
"type": "CVSS_V4"
}
],
"summary": "Fleet: IP spoofing allows bypassing API rate limiting"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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