CVE-2023-27997Known exploitationPublic exploitNetwork attack vector

Pre-authentication code execution via length-unit mismatch

Published Jun 13, 2023 · Updated Jul 31, 2026

Heap-based buffer overflow in affected Fortinet FortiOS and FortiProxy SSL-VPN releases allows remote attackers to execute arbitrary code. The SSL-VPN request decoder compares a hexadecimal character count with a decrypted byte length, then XOR-decrypts beyond its allocated heap buffer. Exploitation requires SSL-VPN to be enabled and reaches code execution as root before authentication; malformed attempts can crash sslvpnd.

CVSS severity9.8
Critical
EPSS probability85.69%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in affected Fortinet FortiOS and FortiProxy SSL-VPN releases allows remote attackers to execute arbitrary code. The SSL-VPN request decoder compares a hexadecimal character count with a decrypted byte length, then XOR-decrypts beyond its allocated heap buffer. Exploitation requires SSL-VPN to be enabled and reaches code execution as root before authentication; malformed attempts can crash sslvpnd.

The record

CVE
CVE-2023-27997
Published
Jun 13, 2023
Updated
Jul 31, 2026
Vendor
Fortinet
Product
FortiOS-6K7K
Classifications
CWE-787, CWE-122, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 13, 2023CVE publishedPublication date reported by the CVE source.
  2. Jul 31, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.0.10
  2. Affected versionversion=6.0.12 <=6.0.16
  3. Affected versionversion=6.2.4
  4. Affected versionversion=6.2.6 <=6.2.7
  5. Affected versionversion=6.2.9 <=6.2.13
  6. Affected versionversion=6.4.10
  7. Affected versionversion=6.4.12
  8. Affected versionversion=6.4.2
  9. Affected versionversion=6.4.6
  10. Affected versionversion=6.4.8
  11. Affected versionversion=7.0.10
  12. Affected versionversion=7.0.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Fortinet · FortiOS-6K7Kversion=6.0.10; version=6.0.12 <=6.0.16; version=6.2.4; version=6.2.6 <=6.2.7; version=6.2.9 <=6.2.13; version=6.4.10; version=6.4.12; version=6.4.2; version=6.4.6; version=6.4.8; version=7.0.10; version=7.0.5
Fortinet · FortiOSversion=6.0.0 <=6.0.16; version=6.2.0 <=6.2.13; version=6.4.0 <=6.4.12; version=7.0.0 <=7.0.11; version=7.2.0 <=7.2.4
Fortinet · FortiProxyversion=1.1.0 <=1.1.6; version=1.2.0 <=1.2.13; version=2.0.0 <=2.0.12; version=7.0.0 <=7.0.9; version=7.2.0 <=7.2.3

Published CVSS scores

9.2FortinetCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:X/RC:R
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-122Heap-based Buffer Overflow
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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