Home/CVE/Fortinet FortiOS and FortiProxy SSL-VPN Heap-Based Buffer Overflow Vulnerability
CVE

CVE-2023-27997

Fortinet FortiOS and FortiProxy SSL-VPN Heap-Based Buffer Overflow Vulnerability

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.

CRITICAL · CVSS 9.8 ⚠ CISA KEV EPSS 0.9212 Ransomware: known
Act now
  • Listed on CISA KEV (known exploited in the wild)
  • Linked to known ransomware campaigns
  • SSVC exploitation status: active
  • EPSS ≥ 0.50 - high probability of exploitation in the next 30 days
  • EPSS percentile: top 0% of all CVEs by exploitation likelihood
  • SSVC automatable: yes - attacks can be scripted at scale
  • CVSS base score ≥ 7.0
Sigma rules10 YARA rules0
⬢

Required Remediation

Apply updates per vendor instructions.

◆

Threat Actors Linked

3
actorMirrorFace
actorPlay
actorVolt Typhoon
⬡

Weakness Classification

CWE-122Heap-based Buffer Overflow
CWE-787Out-of-bounds Write
▤

Affected Products & Versions

13
fortinet fortiproxy>= 1.1.0 and <= 1.1.6
fortinet fortiproxy>= 1.2.0 and <= 1.2.13
fortinet fortiproxy>= 2.0.0 and <= 2.0.12
fortinet fortiproxy>= 7.0.0 and <= 7.0.9
fortinet fortiproxy>= 7.2.0 and <= 7.2.3
fortinet fortios>= 6.0.0 and <= 6.0.16
fortinet fortios>= 6.2.0 and <= 6.2.13
fortinet fortios>= 6.4.0 and <= 6.4.12
◈

Detection Rules (IDS/IPS)

7
et-openET EXPLOIT Fortigate VPN - Repeated GET Requests to /remote/hostcheck_validate (CVE-2023-27997)attempted-admin
et-openET EXPLOIT Fortigate VPN - Repeated POST Requests to /remote/hostcheck_validate (CVE-2023-27997) M1attempted-admin
et-openET EXPLOIT Fortigate VPN - Repeated POST Requests to /remote/hostcheck_validate (CVE-2023-27997) M2attempted-admin
et-openET EXPLOIT Fortigate VPN - Repeated GET Requests to /remote/logincheck (CVE-2023-27997)attempted-admin
et-openET EXPLOIT Fortigate VPN - Repeated POST Requests to /remote/logincheck (CVE-2023-27997)attempted-admin
et-openET EXPLOIT Fortigate VPN - Request to /remote/info - Possible CVE-2023-27997 Exploit Attemptattempted-admin
Open rulesets (ET Open, Snort Community, abuse.ch) link to source. Commercial rulesets are reference-only.
◈

Sigma Hunt Rules

10
Exact rules name this CVE ID. Product rules name an affected product in their title. Related rules cover techniques used by actors who exploited this CVE. Showing the most relevant matches; the complete related set is on the full drill-down.
relatedcriticalAntivirus Exploitation Framework Detection
relatedcriticalAntivirus Password Dumper Detection
relatedcriticalAntivirus Ransomware Detection
relatedcriticalLinux Reverse Shell Indicator
relatedcriticalWebshell Remote Command Execution
relatedcriticalPossible Coin Miner CPU Priority Param
▣

Scoring & Timeline

9.8
CRITICAL · CVSS v3.1 · psirt@fortinet.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD13 Jun 2023 · 09:15 AM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC triage · cisa-vulnrichment
Exploitation
active
Automatable
yes
Technical impact
total
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

4
siemens-csafSSA-770770
siemens-csafSSA-366067
cisaKEV-CVE-2023-27997
cisa-csafcisa-csaf-csaf_files-OT-white-2025-icsa-25-044-06
🔗

References & Sources

2
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://fortiguard.com/psirt/FG-IR-23-097Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-27997US Government Resource
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