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FortisandboxApplication · Fortinet

CVE-2026-59835

HIGH · 8.6 CVSS v3.1 Published 2026-07-14
Fix available
A fix is available. Upgrade to 4.4.9 / 5.0.3 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 5 weeks old

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 · unedited
A exposure of resource to wrong sphere vulnerability in Fortinet FortiSandbox 5.0.0 through 5.0.2, FortiSandbox 4.4.3 through 4.4.8 may allow an unauthenticated attacker to access the VNC server of VMs performing scanning via network requests.

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 confidence

FortiSandbox versions 5.0.0-5.0.2 and 4.4.3-4.4.8 contain an authentication bypass allowing unauthenticated remote attackers to access the VNC server of virtual machines used for malware scanning via network requests. This exposes internal VM consoles that should be restricted to the local management plane.

MitigationApply vendor-supplied patches/updates to FortiSandbox firmware and implement network segmentation to restrict VNC and management interfaces to trusted networks only.

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
FortisandboxApplication
Affected:>= 4.4.3, < 4.4.9>= 5.0.0, < 5.0.3

CVSS 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
High
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L

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 checks

Work through these to decide whether this CVE applies to you.

  1. Check FortiSandbox firmware version
    Access the FortiSandbox web UI (System > Firmware) or run 'get system status' in CLI to retrieve the installed version
    Affected if Version is 4.4.3 through 4.4.8, or 5.0.0 through 5.0.2 (falls within <4.4.9 or <5.0.3)
  2. Identify VNC service listeners
    Run 'netstat -tuln | grep -E "590[0-9]|5900"' or 'show system interface' in CLI to check for VNC port listeners on the appliance
    Affected if VNC ports (5900+) are shown as listening on any interface
  3. Verify VNC network exposure
    From an external host, run 'nmap -p 5900-5910 <fortisandbox-ip>' or attempt a VNC connection to the appliance IP to confirm accessibility
    Affected if VNC ports respond to connections from untrusted/network segments
  4. Review network firewall policy
    In FortiSandbox UI, go to Policy & Objects > Firewall Policy or run 'show firewall policy' in CLI to examine which interfaces can reach VNC services
    Affected if Firewall rules allow traffic from non-management zones to VNC ports

The environment is affected if FortiSandbox version is 4.4.3-4.4.8 or 5.0.0-5.0.2 AND the VNC service is exposed to accessible network interfaces without authentication restrictions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 4.4.9 / 5.0.3 or later
Fixed in 4.4.95.0.3
Interim mitigation

Apply vendor-supplied patches/updates to FortiSandbox firmware and implement network segmentation to restrict VNC and management interfaces to trusted networks only.

Recommended fix High confidence

FortiSandbox 4.4.9 or 5.0.3 (depending on your current major version branch)

  1. 1. Backup current FortiSandbox configuration and any important data
  2. 2. Download FortiSandbox firmware version 4.4.9 (for 4.x installations) or 5.0.3 (for 5.x installations) from Fortinet support portal
  3. 3. Access FortiSandbox admin interface or CLI
  4. 4. Upload and install the firmware upgrade following standard FortiSandbox upgrade procedures
  5. 5. After reboot, verify the upgrade was successful and the vulnerability is resolved
  6. 6. Confirm VNC server is no longer exposed to unauthenticated network access

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fortisandbox Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,544.

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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 sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-59835 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data