CVE-2023-27100Public exploitNetwork attack vector

Brute-force bypass via untrusted proxy headers

Published Mar 22, 2023 · Updated Feb 25, 2025

SSHGuard bypass in Netgate pfSense Plus 22.05.1 and earlier and pfSense CE 2.6.0 and earlier lets remote attackers continue GUI login attempts. Failed WebGUI log entries append attacker-controlled X-Forwarded-For or Client-IP values after the source address, causing the SSHGuard parser to miss that address. The WebGUI must be reachable, and the bypass disables source-address blocking but does not itself authenticate the attacker.

CVSS severity9.8
Critical
EPSS probability9.84%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SSHGuard bypass in Netgate pfSense Plus 22.05.1 and earlier and pfSense CE 2.6.0 and earlier lets remote attackers continue GUI login attempts. Failed WebGUI log entries append attacker-controlled X-Forwarded-For or Client-IP values after the source address, causing the SSHGuard parser to miss that address. The WebGUI must be reachable, and the bypass disables source-address blocking but does not itself authenticate the attacker.

The record

CVE
CVE-2023-27100
Published
Mar 22, 2023
Updated
Feb 25, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-307, T1110.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 22, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 25, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8CISA-ADPCVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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 exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-307Improper Restriction of Excessive Authentication Attempts
T1110.001Brute Force: Password Guessing

Public exploit references

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

Technologies

Your stack

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Your stack

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