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🛡️ CVE-2026-46356 — fleet

🟠 CVSS 7.5 — High ✅ No Known Exploit CWE-290 NVD
7.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Fleet: IP spoofing allows bypassing API rate limiting

Summary

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](mailto:[email protected])

Join #fleet in [osquery Slack](https://join.slack.com/t/osquery/shared_invite/zt-h29zm0gk-s2DBtGUTW4CFel0f0IjTEw)

Credits

We thank @fuzzztf for responsibly reporting this issue.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity high, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: None.

Weakness class

CVE-2026-46356 is classified as CWE-290: Authentication Bypass by Spoofing. Identity is inferred from something an attacker can forge, such as a header or address.

Affected software

CVE-2026-46356 is recorded against 2 packages.

  • fleet (fixed in 4.80.1)
  • github.com/fleetdm/fleet/v4

Timeline and source

Published on 14 May 2026 and last revised on 17 June 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com
github.com

Other advisories for this package

fleet has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-290: Authentication Bypass by Spoofing) in other software:

Details

Severity HIGH
CVSS Score 7.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CWE CWE-290
Public Exploit ✅ No
Source NVD
Published 2026-05-14
Updated 2026-08-20
Modified 2026-06-17
Fix URL N/A

Affected Packages

Software From version Fixed in
fleet — 4.80.1
github.com/fleetdm/fleet/v4 — —

Similar Threats

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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