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CVE-2026-46356 high CVSS 7.5

Vulnerability in github.com/fleetdm/fleet (CVE-2026-46356)

Summary

Vulnerability in github.com/fleetdm/fleet (CVE-2026-46356). Data can be tampered with by attackers. Mitigation: upgrade to 4.80.1 or later.

Original description

The description as published by the source.

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
Join #fleet in […

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-46356 has been found in github.com/fleetdm/fleet.
Data can be tampered with by attackers. CVSS score: 7.5/10.
What to do: upgrade github.com/fleetdm/fleet to 4.80.1 or later.
If unsure, ask your IT team or search "github.com/fleetdm/fleet CVE-2026-46356" on the vendor's site.

CVE-2026-46356 (github.com/fleetdm/fleet) — CWE-290 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 4.80.1 — apply immediately
Workaround: 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 l
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-290) exists in github.com/fleetdm/fleet.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/fleetdm/fleet.

🔥 Severity

Severity: High (CVSS 7.5/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 4.80.1.

🛡️ Workaround

Workaround: 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 l

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/fleetdm/fleet' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'github.com/fleetdm/fleet' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で github.com/fleetdm/fleet を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply temporary workaround mitigate 
    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 l

    パッチが適用されるまでの応急処置として、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 l を実施。回避策の副作用 (機能低下) を確認した上で。

  3. 3
    Apply patch patch 
    Upgrade github.com/fleetdm/fleet to 4.80.1

    ステージング環境で 4.80.1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  4. 4
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

go github.com/fleetdm/fleet
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.80.1"}]}]
go github.com/fleetdm/fleet/v4
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.80.1"}]}]

References

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