CVE-2026-24000: Fleet has a rate limiting bypass via untrusted client IP headers
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:
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Credits
We thank @fuzzztf for responsibly reporting this issue.
Other sources
Fleet is open source device management software. Prior to version 4.80.1, 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, and/or 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. Version 4.80.1 contains a patch. As a workaround, run Fleet behind a trusted reverse proxy or load balancer that overwrites client IP headers.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-24000?
CVE-2026-24000 has a medium severity level due to its potential to allow IP address spoofing and bypassing of rate limiting controls.
How do I fix CVE-2026-24000?
To fix CVE-2026-24000, upgrade to Fleet version 4.80.1 or later where this vulnerability has been resolved.
What versions of Fleet are affected by CVE-2026-24000?
CVE-2026-24000 affects Fleet versions prior to 4.80.1.
How does CVE-2026-24000 impact security?
CVE-2026-24000 compromises security by allowing clients to spoof their IP addresses, which can lead to abusive behavior and bypass rate limiting.
Can CVE-2026-24000 be exploited by unauthenticated users?
Yes, CVE-2026-24000 can be exploited by both authenticated and unauthenticated users.