⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Medium · CVSS 6.7

How to Fix CVE-2026-25836: Execute unauthorized code or commands in FortiSandbox Cloud

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 6.7, Medium
Actively exploited?No
AffectedFortinet FortiSandbox Cloud (5.0.4); Fortinet FortiSandbox PaaS (5.0.4)
Fixed inSee vendor advisory
Type (CWE)CWE-78: Execute unauthorized code or commands

What is CVE-2026-25836?

An improper neutralization of special elements used in an os command ('os command injection') vulnerability in Fortinet FortiSandbox Cloud 5.0.4, FortiSandbox PaaS 5.0.4 may allow a privileged attacker with super-admin profile and CLI access to execute unauthorized code or commands via crafted HTTP requests.

In practical terms, a successful attacker gets command injection on the host operating system. There is no confirmed in-the-wild exploitation listed in CISA's KEV catalog at the time of writing, but the CVSS rating still warrants prompt patching.

Am I affected?

You're affected if you run Fortinet FortiSandbox Cloud at any version in the Affected row above. Use these probes to find your installed build:


get system status

How to fix CVE-2026-25836

The primary fix is to upgrade to the patched build listed in the Fixed in row above (See vendor advisory). Pick the platform that matches your install and run the commands below.

FortiOS / FortiGate (CLI)


# Vendor advisory: https://fortiguard.fortinet.com/psirt/FG-IR-26-096
get system status
execute backup config tftp config-backup.conf 10.0.0.10
execute restore image tftp FGT_<patched-version>.out 10.0.0.10
# Device reboots automatically after image restore

PowerShell script (Windows) - detect, back up, upgrade, verify, log


# Vendor advisory: https://fortiguard.fortinet.com/psirt/FG-IR-26-096
# Run as Administrator
$ErrorActionPreference = 'Stop'
$log = "$env:ProgramData\FortiSandboxCloud-Patch-CVE-2026-25836.log"
function Write-Log($msg) { "$(Get-Date -Format s)  $msg" | Tee-Object -FilePath $log -Append }

Write-Log "Starting CVE-2026-25836 remediation for Fortinet FortiSandbox Cloud"

# 1. Detect: replace the path/version probe with one valid for your install
$installed = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*FortiSandbox*' } |
    Select-Object -First 1 -ExpandProperty Version)
Write-Log "Detected version: $installed"

if (-not $installed) {
    Write-Log "Product not installed on this host; nothing to do."
    return
}
if ([version]$installed -ge [version]'<patched-version>') {
    Write-Log "Already at fixed version $installed; no action needed."
    return
}

# 2. Backup configuration to a timestamped folder
$backup = "$env:ProgramData\FortiSandboxCloud-Backup-$(Get-Date -Format yyyyMMdd-HHmm)"
New-Item -ItemType Directory -Path $backup -Force | Out-Null
# Adjust the source path to match your install
$src = "$env:ProgramFiles\Fortinet\FortiSandbox Cloud"
if (Test-Path $src) { Copy-Item -Path $src -Destination $backup -Recurse -Force }
Write-Log "Backed up config to $backup"

# 3. Apply the patched installer (place the verified file on a share or staging path)
$installer = "$env:TEMP\FortiSandboxCloud-<patched-version>.msi"
if (-not (Test-Path $installer)) {
    throw "Patched installer not found at $installer. Stage it from your software repo first."
}
Start-Process msiexec.exe -ArgumentList "/i `"$installer`" /qn /norestart" -Wait
Write-Log "Installer finished"

# 4. Verify
$verify = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*FortiSandbox*' } |
    Select-Object -First 1 -ExpandProperty Version)
if ([version]$verify -ge [version]'<patched-version>') {
    Write-Log "SUCCESS: now at $verify (>= <patched-version>)"
} else {
    Write-Log "FAILURE: still at $verify after install"
    exit 1
}

Bash script (Linux) - detect, back up, upgrade, verify, log


# Vendor advisory: https://fortiguard.fortinet.com/psirt/FG-IR-26-096
#!/usr/bin/env bash
set -euo pipefail
LOG=/var/log/fortisandbox-cloud-patch-cve-2026-25836.log
log()  { echo "$(date -Iseconds)  $*" | tee -a "$LOG"; }

log "Starting CVE-2026-25836 remediation for Fortinet FortiSandbox Cloud"

# 1. Detect installed version (works for deb and rpm packages)
if command -v dpkg >/dev/null && dpkg -s fortisandbox-cloud >/dev/null 2>&1; then
    CURRENT=$(dpkg-query -W -f='${Version}' fortisandbox-cloud)
    PKG_MGR=apt
elif command -v rpm >/dev/null && rpm -q fortisandbox-cloud >/dev/null 2>&1; then
    CURRENT=$(rpm -q --queryformat '%{VERSION}' fortisandbox-cloud)
    PKG_MGR=dnf
else
    log "fortisandbox-cloud not installed via apt or rpm; check your package manager or vendor instructions."
    exit 0
fi
log "Detected: fortisandbox-cloud=$CURRENT (manager=$PKG_MGR)"

# 2. Backup config
BACKUP=/var/backups/fortisandbox-cloud-$(date +%Y%m%d-%H%M)
mkdir -p "$BACKUP"
for d in /etc/fortisandbox-cloud /etc/${pkg%%-*} ; do
    [ -d "$d" ] && cp -a "$d" "$BACKUP/" && log "Backed up $d to $BACKUP"
done

# 3. Upgrade
if [ "$PKG_MGR" = apt ]; then
    sudo apt-get update -y
    sudo apt-get install --only-upgrade -y fortisandbox-cloud
else
    sudo dnf upgrade --security -y fortisandbox-cloud
fi

# 4. Verify
if [ "$PKG_MGR" = apt ]; then
    NEW=$(dpkg-query -W -f='${Version}' fortisandbox-cloud)
else
    NEW=$(rpm -q --queryformat '%{VERSION}' fortisandbox-cloud)
fi
log "After upgrade: $NEW"

# Optionally compare against <patched-version> with dpkg --compare-versions or sort -V
log "Done. Restart the affected service if the package install did not."

If you can't patch immediately

These are runnable hardening commands. They reduce blast radius but they're not a replacement for the vendor patch.

Block external access to the affected service

Apply a perimeter ACL so the exploitable port is only reachable from administrative subnets:


# Vendor advisory: https://fortiguard.fortinet.com/psirt/FG-IR-26-096
# Example Cisco ACL on the upstream router
access-list 110 permit tcp 10.0.0.0 0.0.0.255 host <appliance-ip> eq 443
access-list 110 deny   tcp any host <appliance-ip> eq 443 log
interface GigabitEthernet0/0
 ip access-group 110 in

Rate-limit and log the affected endpoint at the reverse proxy


limit_req_zone $binary_remote_addr zone=admin:10m rate=10r/m;
location /<vulnerable-path> {
    limit_req zone=admin burst=5 nodelay;
    access_log /var/log/nginx/admin-access.log combined;
    proxy_pass http://backend;
}

How to verify the fix worked

Run the version probe again and confirm the running build matches the Fixed in row above.


get system status

Expected output: a Version: FortiGate-... vthe patched build line (or higher build number).

Then re-run any vulnerability scanner you used previously and confirm the finding for CVE-2026-25836 has cleared. Sweep your logs for the indicators of compromise listed in the vendor or CISA advisory, especially if the system was internet-reachable during the disclosure window.

Frequently asked questions

Is CVE-2026-25836 being actively exploited?

Not at the time of writing. It is not listed in CISA's Known Exploited Vulnerabilities catalog. That status can change, so monitor the vendor advisory and the KEV catalog if the system is exposed.

How severe is CVE-2026-25836?

CVSS rates it 6.7 (Medium). Use that score to set your patch priority next to the other items in your queue.

Do I have to take FortiSandbox Cloud offline to apply the patch?

It depends on the deployment. High-availability or clustered installs can usually patch one node at a time with no full outage. Standalone installs typically need a short restart. Always follow the vendor's documented upgrade steps.

What if my vulnerability scanner still flags CVE-2026-25836 after I patch?

Re-run the scan after a service restart, then confirm the scanner's plugin set is up to date. Some scanners detect by banner version only and lag the official fix metadata by a release.

References

*Written by Sai Kiran Pandrala on 2026-05-25. Sourced from the official vendor advisory, the NVD record, and the CISA KEV listing. Always confirm against the vendor advisory before applying changes in production.*