Exploited CVEs / Fortinet / CVE-2023-27997
CVE-2023-27997
Fortinet FortiOS and FortiProxy SSL-VPN Heap-Based Buffer Overflow Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted, and the vulnerability is known to be used in ransomware campaigns. Federal agencies were required to remediate by 2023-07-04 (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.
Actively exploited Fortinet FortiOS and FortiProxy SSL-VPN vulnerability, Critical severity, CVSS 9.8. Added to the CISA KEV catalog 2023-06-13.
Risk summary
Updated July 26, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
Senserva AI Opinion for CVE-2023-27997
This is a heap-based buffer overflow in Fortinet FortiOS and FortiProxy SSL-VPN that lets an unauthenticated remote attacker run code by sending crafted requests, meaning your VPN gateway can be taken over before anyone logs in. Any organization exposing FortiGate SSL-VPN to the internet is directly reachable, and this one is confirmed in CISA KEV with an 86 percent EPSS score and documented ransomware use. Severity is Critical (CVSS 9.8), so pre-authentication access to the perimeter device makes this a top-priority fix.
Do this: Identify all internet-facing FortiOS and FortiProxy SSL-VPN instances and apply Fortinet's patched firmware immediately, disabling SSL-VPN where you cannot patch today.
AI-generated from public data, 2026-07-22. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2023-27997
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for CVE-2023-27997
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.
CISA required action
Federal (BOD 22-01) remediation due date: 2023-07-04 (past due).
Apply updates per vendor instructions.
Official fix for CVE-2023-27997
The authoritative fix and affected-version list are published by the vendor. Find the FortiOS and FortiProxy SSL-VPN advisory on Fortinet PSIRT Advisories.
Common questions about CVE-2023-27997
Is CVE-2023-27997 actively exploited?
Yes. CVE-2023-27997 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2023-06-13, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 86%. CISA also reports it is known to be used in ransomware campaigns.
What is the CISA deadline and required action for CVE-2023-27997?
CISA set the federal (BOD 22-01) remediation due date at 2023-07-04, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.
What fixes CVE-2023-27997?
The authoritative fix is in the vendor advisory: see Fortinet PSIRT Advisories for the patched FortiOS and FortiProxy SSL-VPN 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-2023-27997?
Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2023-27997'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).
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Authoritative references
Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.
