CVE-2023-27100
Published: 22 March 2023
Summary
CVE-2023-27100 is a critical-severity Improper Restriction of Excessive Authentication Attempts (CWE-307) vulnerability in Netgate Pfsense Plus. Its CVSS base score is 9.8 (Critical).
Operationally, ranked in the top 13.0% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
Deeper analysis
CVE-2023-27100 is an improper restriction of excessive authentication attempts vulnerability (CWE-307) residing in the SSHGuard component of Netgate pfSense Plus software version 22.05.1 and pfSense CE software version 2.6.0. The flaw permits bypass of brute-force protection mechanisms through specially crafted web requests and carries a CVSS 3.1 base score of 9.8 reflecting network-exploitable conditions with no required privileges or user interaction.
An unauthenticated remote attacker can submit crafted requests to evade SSHGuard rate limiting, thereby enabling unrestricted authentication attempts against the affected pfSense instance and potentially leading to full compromise of confidentiality, integrity, and availability.
Netgate has published security advisory pfSense-SA-23_05.sshguard and a corresponding Redmine issue that address the flaw; the advisory and associated patches are available at the listed Netgate URLs. The EPSS score for this CVE rose from a low baseline to a peak of 0.0610 on 2026-04-12 before receding to the current value of 0.0305.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2023-30884
Vulnerability details
Improper restriction of excessive authentication attempts in the SSHGuard component of Netgate pfSense Plus software v22.05.1 and pfSense CE software v2.6.0 allows attackers to bypass brute force protection mechanisms via crafted web requests.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
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.
This control directly enforces limits on consecutive invalid logon attempts and automatic response (e.g., lockout) to prevent brute-force exploitation of authentication mechanisms.
Specific conditions can include excessive failed attempts, triggering stronger authentication that restricts brute-force exploitation.