Exploited CVEs / Fortinet / CVE-2026-39808

CVE-2026-39808

Fortinet FortiSandbox OS Command Injection Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2026-07-19 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Fortinet PSIRT Advisories, linked below.

Risk summary

CriticalCISA KEV

9.8

CVSS base

91%

EPSS exploit probability

Critical

Severity

2026-07-16

Added to KEV

2026-07-19 (past due)

CISA due date

Actively exploited Fortinet FortiSandbox vulnerability, Critical severity, CVSS 9.8. Added to the CISA KEV catalog 2026-07-16.

Senserva AI read on CVE-2026-39808 CISA required action Official fix for CVE-2026-39808 Admin questions

Senserva AI Opinion for CVE-2026-39808

This is an unauthenticated OS command injection in Fortinet FortiSandbox, reachable through crafted HTTP requests with no credentials needed, and it carries a Severity of Critical (CVSS 9.8) with a 90 percent EPSS exploit probability. CISA confirmed active exploitation and added it to the KEV catalog on 2026-07-16, so any FortiSandbox with an exposed management or web interface is a live target. Because FortiSandbox inspects suspected malware, a compromise hands attackers control of a device that already sees your threat traffic.

Do this: Identify all FortiSandbox appliances, apply Fortinet's fixed release now, and remove any HTTP/management interface exposure from untrusted networks until patched.

AI-generated from public data, 2026-07-25. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2026-39808

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2026-39808, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2026-39808.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2026-39808: Fortinet FortiSandbox OS Command Injection Vulnerability
- Affected: Fortinet FortiSandbox
- Severity: Critical, CVSS 9.8; EPSS 30-day exploitation probability 91%
- Added to CISA KEV: 2026-07-16; federal remediation due 2026-07-19
- Ransomware-linked: no
- 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 dis...
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch now

Exploited in the wild: confirmed by the CISA KEV catalog, not predicted.

The fix ships from the vendor: Fortinet PSIRT Advisories.

Do this now: Federal remediation deadline 2026-07-19; treat it as your outer bound. Patch now and verify deployment on every exposed device.

Updated August 15, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2026-39808

Published: 2026-07-16
Last revised: 2026-07-16
Changes tracked: 1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one

What changed, and when

The strongest signal is CVE-2026-39808's addition to the CISA KEV catalog on 2026-07-16, confirming active exploitation. The next day the CVSS Severity jumped from 0.0 to 9.8 and EPSS started at 84.2%, then climbed to 89.7% on 2026-07-24 and 91.2% on 2026-08-07. The steady upward direction means you should prioritize remediation today.

Drawn by Senserva Vivid from the Senserva change record. Hover any point for its date and value.

2026-07-16 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 9.8; EPSS first scored at 84.2%
2026-07-24 EPSS 84.2% to 89.7%
2026-08-07 EPSS 89.7% to 91.2%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2026-07-19 (past due).

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.

Official fix for CVE-2026-39808

The authoritative fix and affected-version list are published by the vendor. Find the FortiSandbox advisory on Fortinet PSIRT Advisories.

Fortinet PSIRT Advisories CISA KEV entry

Common questions about CVE-2026-39808

Is CVE-2026-39808 actively exploited?

Yes. CVE-2026-39808 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2026-07-16, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 91%.

What is the CISA deadline and required action for CVE-2026-39808?

CISA set the federal (BOD 22-01) remediation due date at 2026-07-19, which has passed; treat any unremediated system as overdue. The verbatim 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.

What fixes CVE-2026-39808?

The authoritative fix is in the vendor advisory: see Fortinet PSIRT Advisories for the patched FortiSandbox versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2026-39808?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2026-39808's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

Scope and sources

More exploited Fortinet CVEs: CVE-2025-68686 CVE-2026-25089 CVE-2026-21643 CVE-2026-35616 CVE-2026-24858 CVE-2025-59718 CVE-2025-58034 CVE-2025-64446
All Fortinet exploited CVEs on one page: Fortinet vulnerabilities actively exploited.
Authoritative references: CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.