HIGH CVSS 7.5
Published: 2026-05-14

CVE-2026-46356

fleetdm fleet Security Advisory (CVE-2026-46356)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-46356 impacting fleetdm fleet. Evaluated with CVSS Base Score of 7.5 (HIGH).

Original NVD Description

Source: NIST NVD
Fleet 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.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
Low (AC:L)
No specialized conditions required
Privileges Required
None (PR:N)
Unauthenticated execution
User Interaction
None (UI:N)
Zero human interaction required
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
High (I:H)
Total modification of target system
Availability
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product fleetdm / fleet
Affected Versions *
Weakness Enumeration CWE-290

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2026-46356 impacting fleetdm fleet.

⚡ Nuclei Detection Template (YAML) cve-2026-46356.yaml
id: cve-2026-46356

info:
  name: fleetdm fleet - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-46356 affecting fleetdm fleet.
    Evaluation: Fleet is open source device management software. Prior to version 4.80.1, a vulnerability in Fleet's IP extraction logic allows unauthenticated a...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-46356
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
    cvss-score: 7.5
    cve-id: CVE-2026-46356
    cwe-id: CWE-290
  tags: cve,cve-2026-46356,fleetdm,fleet,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "fleet"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-46356.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-46356
# Target: fleetdm fleet | CVSS: 7.5 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-46356 (fleetdm fleet)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against fleetdm fleet scope (*).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2026-46356.sh
# Recommended Remediation & Patching Commands for CVE-2026-46356
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install fleet 2>/dev/null || \
sudo dnf upgrade fleet 2>/dev/null || \
sudo yum update fleet

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i fleet 2>/dev/null || rpm -qa | grep -i fleet

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

🔗 Verified Technical References

Authorities
  • No records filed in this category.
Distributions
  • No records filed in this category.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-46356 in fleetdm fleet?

Review vendor-specific security notices and update fleetdm fleet packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2026-46356?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2026-46356?

CVE-2026-46356 is classified with a CVSS 3.1 Base Score of 7.5 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
7.5
HIGH SEVERITY
CVE ID CVE-2026-46356
Weakness CWE-290
Vendor fleetdm
Product fleet
Published 2026-05-14
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N