EUVD-2026-30373
GHSA-j8h8-75h3-jg53
CVSS VectorNVD
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
5DescriptionNVD
Impact
Fleet trusted client-supplied IP address headers when determining the source IP for incoming requests. This allowed authenticated and unauthenticated clients to spoof their apparent IP address and bypass per-IP rate limiting controls.
Fleet determines a client’s public IP address using HTTP headers such as:
- X-Forwarded-For
- X-Real-IP
- True-Client-IP
These headers were trusted without validation. An attacker could supply arbitrary values in these headers, causing Fleet to treat each request as originating from a different IP address.
This could allow an attacker to bypass per-IP rate limits and increase the effectiveness of brute-force or password-spraying attempts against authentication endpoints.
This issue does not allow authentication bypass, privilege escalation, data exposure, or remote code execution on its own.
Workarounds
Run Fleet behind a trusted reverse proxy or load balancer that overwrites client IP headers.
For more information
If you have any questions or comments about this advisory:
Email us at [security@fleetdm.com](mailto:security@fleetdm.com) Join #fleet in osquery Slack
Credits
We thank @fuzzztf for responsibly reporting this issue.
AnalysisAI
Fleet trusts untrusted client-supplied IP address headers (X-Forwarded-For, X-Real-IP, True-Client-IP) when determining source IP for incoming requests, allowing both authenticated and unauthenticated attackers to spoof their apparent IP address and bypass per-IP rate limiting controls. This enables brute-force and password-spraying attacks against authentication endpoints to scale without triggering rate-limit protections, though the vulnerability does not itself enable authentication bypass, privilege escalation, data exposure, or remote code execution.
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External POC / Exploit Code
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