Security Resilience

CVE-2023-26208

Fortinet Fortiauthenticator 5.4.0 – 6.5.0

Published
09 March 2023
Modified
21 November 2024
Patch / advisory
View advisory
CVSS Score v3.1 3.7
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
EPSS Score 0.018 78th percentile
Risk Priority 45 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2023-26208 is a low-severity Improper Restriction of Excessive Authentication Attempts (CWE-307) vulnerability in Fortinet Fortiauthenticator. Its CVSS base score is 3.7 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Password Guessing (T1110.001); ranked in the top 22% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2023-26208 is an improper restriction of excessive authentication attempts vulnerability, tracked as CWE-307, that affects Fortinet FortiAuthenticator versions 6.4.x and earlier. The flaw resides in the login form and permits a remote attacker to submit repeated HTTP requests that partially exhaust CPU and memory resources on the affected system. Its CVSS 3.1 base score is 3.7, reflecting network attack vector, high attack complexity, and limited impact on availability.

A remote unauthenticated attacker can exploit the weakness simply by generating numerous HTTP requests against the login form, resulting in partial resource exhaustion without any authentication or user interaction required.

The official FortiGuard advisory FG-IR-20-078, referenced at https://fortiguard.com/psirt/FG-IR-20-078, addresses the issue for supported FortiAuthenticator releases. The EPSS score remains flat at 0.1970 with no material increase after disclosure.

OWASP Top 10 for Web (2025)

A07:2025 Authentication Failures

EU & UK References

Vulnerability Data

A improper restriction of excessive authentication attempts vulnerability [CWE-307] in Fortinet FortiAuthenticator 6.4.x and before allows a remote unauthenticated attacker to partially exhaust CPU and memory via sending numerous HTTP requests to the login form.

CWE(s)
CWE-307

Related Threats

MITRE ATT&CK Enterprise Techniques

T1110.001 Password Guessing Credential Access
Adversaries with no prior knowledge of legitimate credentials within the system or environment may guess passwords to attempt access to accounts.
attack.mitre.org →
T1001.002 Steganography Command And Control
Adversaries may use steganographic techniques to hide command and control traffic to make detection efforts more difficult.
attack.mitre.org →
T1003.002 Security Account Manager Credential Access
Adversaries may attempt to extract credential material from the Security Account Manager (SAM) database either through in-memory techniques or through the Windows Registry where the SAM database is stored.
attack.mitre.org →
T1003.006 DCSync Credential Access
Adversaries may attempt to access credentials and other sensitive information by abusing a Windows Domain Controller's application programming interface (API)(Citation: Microsoft DRSR Dec 2017) (Citation: Microsoft GetNCCChanges) (Citati…
attack.mitre.org →
T1010 Application Window Discovery Discovery
Adversaries may attempt to get a listing of open application windows.
attack.mitre.org →
T1014 Rootkit Stealth
Adversaries may use rootkits to hide the presence of programs, files, network connections, services, drivers, and other system components.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-22629Same vendor: Fortinet
CVE-2025-53379Same product: Fortinet Fortiauthenticator
CVE-2024-45327Same vendor: Fortinet
CVE-2026-21743Same product: Fortinet Fortiauthenticator
CVE-2024-23664Same product: Fortinet Fortiauthenticator
CVE-2025-57823Same product: Fortinet Fortiauthenticator
CVE-2026-44277Same product: Fortinet Fortiauthenticator
CVE-2025-59923Same product: Fortinet Fortiauthenticator
CVE-2024-23106Same vendor: Fortinet
CVE-2023-26209Same vendor: Fortinet

Affected Assets

fortinet
fortiauthenticator
5.4.0 — 6.5.0

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 2 hardening rules · 1 OS baseline
Validate
Prove the fix (OWASP ASVS)

—

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

AC-7 Unsuccessful Logon Attempts
addresses: CWE-307

This control directly enforces limits on consecutive invalid logon attempts and automatic response (e.g., lockout) to prevent brute-force exploitation of authentication mechanisms.

IA-10 Adaptive Authentication
addresses: CWE-307

Specific conditions can include excessive failed attempts, triggering stronger authentication that restricts brute-force exploitation.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

DE.CM-03 partial match
blocks

Behavioral monitoring of authentication activity can detect excessive failed attempts after they occur.

PR.AA-03 partial match
blocks

Authentication enforcement directly includes lockout, throttling, and MFA policies that prevent brute-force attempts.

PR.PS-04 partial match
blocks

Generating auth logs enables later detection or forensics but does not itself restrict attempts.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.14 Information transfer partial match
removes
A.5.15 Access control partial match
removes
A.5.16 Identity management partial match
removes
A.5.17 Authentication information partial match
removes
A.5.18 Access rights partial match
removes
A.8.10 Information deletion partial match
removes

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (higher-evidence rows only; rows rated `none` are excluded).

RHEL 7 (2 rules)
  • V-204427 The Red Hat Enterprise Linux operating system must be configured to lock accounts for a minimum of 15 minutes after three unsuccessful logon attempts within a 15-minute timeframe. blocks CWE-307
  • V-204428 The Red Hat Enterprise Linux operating system must lock the associated account after three unsuccessful root logon attempts are made within a 15-minute period. blocks CWE-307

References