---
title: "CVE-2026-39808: Fortinet FortiSandbox OS Command Injection Vulnerability"
url: https://erroneo.us/security/cve/CVE-2026-39808/
description: "CVE-2026-39808 (Fortinet FortiSandbox): Exploited in the wild (CISA KEV). A improper neutralization of special elements used in an os command ('os command…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-04-14
date_modified: 2026-10-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-39808"
kev: true
cvss: 9.1
epss: 0.47362
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-39808: Fortinet FortiSandbox OS Command Injection Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Fortinet FortiSandbox. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-07-16, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-07-19 ; treat that as the outer limit, not the target.
- EPSS 47.4% , percentile 99: FIRST’s model estimates a 47.4% chance of exploitation activity in the next 30 days, higher than 99% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Act now. FortiSandbox: Two Exploited Pre-Auth Command Injections — If any FortiSandbox runs 4.2, 4.4 below 4.4.9 or 5.0 below 5.0.6, upgrade now and check it for compromise: both bugs need no login, one has a public exploit, and attacks began in June.

## What it is

A improper neutralization of special elements used in an os command ('os command injection') vulnerability in Fortinet FortiSandbox 4.4.0 through 4.4.8 may allow attacker to execute unauthorized code or commands via

## Affected products (CVE record)

- Fortinet FortiSandbox: 4.4.0 <= 4.4.8
- Fortinet FortiSandbox PaaS: 23.4.4374, 23.4.4350, 23.3.4329, 23.1.4245, 22.2.4151, 22.2.4134, 22.1.4113, 21.4.4072, 21.3.4055

## Severity

- fortinet CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C`

## Exploitation

- CISA KEV: added 2026-07-16; federal due date 2026-07-19. Known ransomware use: Unknown.
- CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
- CISA SSVC assessment: exploitation active , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 47.36% probability of exploitation activity in the next 30 days; percentile 99.

## Sources

- [Listed in CISA KEV notes (fortiguard.fortinet.com)](https://fortiguard.fortinet.com/psirt/FG-IR-26-100)
- [CVE.org record CVE-2026-39808](https://www.cve.org/CVERecord?id=CVE-2026-39808)
- [NVD entry CVE-2026-39808](https://nvd.nist.gov/vuln/detail/CVE-2026-39808)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-39808)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk)
- [github.com](https://github.com/samu-delucas/CVE-2026-39808)

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Source page: https://erroneo.us/security/cve/CVE-2026-39808/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt