Cyber 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 77th percentile
Risk Priority 45 floored blend · peak EPSS

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 Brute Force (T1110); ranked in the top 23% 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 Brute Force Credential Access
Adversaries may use brute force techniques to gain access to accounts when passwords are unknown or when password hashes are obtained.
attack.mitre.org →
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 →
T1110.003 Password Spraying Credential Access
Adversaries may use a single or small list of commonly used passwords against many different accounts to attempt to acquire valid account credentials.
attack.mitre.org →
T1110.004 Credential Stuffing Credential Access
Adversaries may use credentials obtained from breach dumps of unrelated accounts to gain access to target accounts through credential overlap.
attack.mitre.org →
T1078 Valid Accounts Stealth
Adversaries may obtain and abuse credentials of existing accounts as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-59923Same product: Fortinet Fortiauthenticator
CVE-2026-44277Same product: Fortinet Fortiauthenticator
CVE-2026-22629Same vendor: Fortinet
CVE-2023-26209Same vendor: Fortinet
CVE-2023-45582Same vendor: Fortinet
CVE-2024-23106Same vendor: Fortinet
CVE-2026-21743Same product: Fortinet Fortiauthenticator
CVE-2025-57823Same product: Fortinet Fortiauthenticator
CVE-2025-53379Same product: Fortinet Fortiauthenticator
CVE-2024-45327Same 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.

PR.AA-03 mostly match
prevents

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

DE.CM-03 partial match
prevents

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

PR.PS-04 partial match
prevents

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.8.5 Secure authentication partial match
prevents

CAPTCHA, account lock-out after repeated failures, and alerts on excessive attempts directly stop automated brute-force guessing of credentials.

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` (authoritative 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. prevents 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. prevents CWE-307

References