CVE-2023-27997
CRITICALCISA KEVEPSS 100th pctlDescription
A heap-based buffer overflow vulnerability [CWE-122] in FortiOS version 7.2.4 and below, version 7.0.11 and below, version 6.4.12 and below, version 6.0.16 and below and FortiProxy version 7.2.3 and below, version 7.0.9 and below, version 2.0.12 and below, version 1.2 all versions, version 1.1 all versions SSL-VPN may allow a remote attacker to execute arbitrary code or commands via specifically crafted requests.
How to fix
Actively exploited, no published fix found yet
CISA required action: Apply updates per vendor instructions.
Federal remediation due: 2023-07-04
Known ransomware campaign use
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploit Intelligence
Very high risk: more likely to be exploited than 100% of all known CVEs.
Fortinet FortiOS and FortiProxy SSL-VPN Heap-Based Buffer Overflow Vulnerability
Fortinet FortiOS and FortiProxy SSL-VPN contain a heap-based buffer overflow vulnerability which can allow an unauthenticated, remote attacker to execute code or commands via specifically crafted requests.
Apply updates per vendor instructions.
Remediation due: 2023-07-04
Associated with ransomware campaigns
References
Related Vulnerabilities
Other CWE-122 (Heap-based Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2015-3113 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2024-26256 | High | 7.8 | 88% | - | Fix |
| CVE-2020-25687 | Medium | 5.9 | 87% | - | Fix |
| CVE-2009-3459 | High | 8.8 | 87% | KEV | Fix |
| CVE-2021-21017 | High | 8.8 | 86% | KEV | - |
| CVE-2020-25683 | Medium | 5.9 | 86% | - | Fix |
Common questions
How do I fix CVE-2023-27997?
No published fix for CVE-2023-27997 has been found yet. It is on the CISA Known Exploited Vulnerabilities list; federal agencies must remediate by 2023-07-04. Apply the vendor's mitigations per CISA's guidance.
Is CVE-2023-27997 being actively exploited?
Yes. CVE-2023-27997 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. CISA has also linked it to known ransomware campaigns. US federal agencies were required to remediate it by 2023-07-04. Treat it as a priority whatever its CVSS score says.
How severe is CVE-2023-27997?
CVE-2023-27997 has a CVSS v3 base score of 9.8, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-31.