CVE-2026-46356
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedFleet is open source device management software. Prior to version 4.80.1, 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. 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. Version 4.80.1 contains a patch. 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceFleet prior to 4.80.1 extracts client IP addresses from unvalidated request headers (X-Forwarded-For, X-Real-IP, True-Client-IP) and uses them as the rate-limiting key. Attackers can spoof these headers to appear as different clients on each request, bypassing per-IP rate limits on login endpoints and enabling brute-force attacks.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 4.80.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check Fleet server versionRun `fleetctl --version` or inspect the Fleet server binary/package version. On the host running Fleet, you can also check via `fleet --version` or look at the Docker container image tag if running containers.Affected if The installed version is earlier than 4.80.1 (e.g., 4.79.0, 4.78.x, etc.)
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Verify rate limiting configuration on login endpointsExamine Fleet's configuration files (typically YAML or environment variables) for rate limiting settings on authentication endpoints. Look for rate_limit settings, particularly around /api/v1/fleet/login or similar login-related routes.Affected if Rate limiting is enabled and configured to use client IP addresses as the limiting key, but the application trusts X-Forwarded-For or similar headers without validation.
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Inspect reverse proxy configurationIf Fleet is deployed behind a reverse proxy (nginx, HAProxy, AWS ALB, etc.), check whether the proxy is configured to overwrite (not append to) X-Forwarded-For headers with the actual client IP. Inspect the proxy configuration for settings like `proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;` versus `$remote_addr`.Affected if The reverse proxy appends to X-Forwarded-For rather than overwriting it, or the proxy does not set X-Forwarded-For at all, allowing clients to inject arbitrary IP values in the header.
You are affected if Fleet version is below 4.80.1 AND rate limiting on login endpoints relies on X-Forwarded-For, X-Real-IP, or True-Client-IP headers without the reverse proxy validating and overwriting those headers with the true client IP.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped4.80.1
Upgrade to Fleet 4.80.1 or deploy Fleet behind a reverse proxy that overwrites X-Forwarded-For headers with the true client IP and apply rate limiting at the proxy/WAF layer.
Fleet 4.80.1
- Backup Fleet configuration and data before upgrading
- Upgrade Fleet to version 4.80.1 or later to apply the patch
- If immediate upgrade is not possible, ensure Fleet is deployed behind a reverse proxy (nginx, Cloudflare, AWS ALB) that overwrites X-Forwarded-For with the true client IP
- Configure rate limiting at the reverse proxy or WAF layer to protect sensitive endpoints such as the login API
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-46356 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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