CVE-2024-55591
Fortinet FortiOS and FortiProxy Authentication Bypass Vulnerability
Fortinet FortiOS and FortiProxy
An Authentication Bypass Using an Alternate Path or Channel vulnerability [CWE-288] affecting FortiOS version 7.0.0 through 7.0.16 and FortiProxy version 7.0.0 through 7.0.19 and 7.2.0 through 7.2.12 allows a remote attacker to gain super-admin privileges via crafted requests to Node.js websocket module.
Ransomware groups exploiting CVE-2024-55591
Qilin ransomware was first observed in July of 2022. Qilin Ransomware is written in Golang and supports multiple encryption modes; all of which are controlled by the operator. Qilin actors practice double extortion – demanding payment for a decryptor, as well
The Gentlemen is a RaaS group that emerged in July–August 2025, rapidly claiming over 320 victims across 17+ countries by offering affiliates a 90% revenue share, deploying a Go-based locker against Windows, Linux, NAS, and BSD systems; a compromised C2 server
DragonForce is a major ransomware-as-a-service operation first observed in August 2023 that launched a formal affiliate program offering 80% revenue share, then rebranded as a "ransomware cartel" in 2025, gaining notoriety for high-profile attacks on UK retail
Exploitation is attributed to these groups across their recorded activity. It does not follow that every organisation they listed was reached through CVE-2024-55591 — the source data does not record an entry point per incident.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 14 January 2025. US federal agencies were required to remediate it by 21 January 2025. CISA records this vulnerability as known to be used in ransomware campaigns.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 98.3%, which is higher than 99.9% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Recent listings by these groups
Disclosures from the groups above, newest first.
Frequently asked questions
Is CVE-2024-55591 being exploited by ransomware groups?
Yes. CVE-2024-55591 is recorded as exploited by Qilin, Thegentlemen, Dragonforce. Between them these groups account for 3,710 victim disclosures in this database. CISA also records this vulnerability as used in ransomware campaigns.
What does CVE-2024-55591 affect?
CVE-2024-55591 affects Fortinet FortiOS and FortiProxy. An Authentication Bypass Using an Alternate Path or Channel vulnerability [CWE-288] affecting FortiOS version 7.0.0 through 7.0.16 and FortiProxy version 7.0.0 through 7.0.19 and 7.2.0 through 7.2.12 allows a remote attacker to gain super-admin privileges via crafted requests to Node.js websocket module.
How severe is CVE-2024-55591?
CVE-2024-55591 is rated CRITICAL with a CVSS base score of 9.8. EPSS puts the probability of exploitation in the next 30 days at 98.3%, higher than 99.9% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 21 January 2025.
How should organisations respond to CVE-2024-55591?
Apply the vendor patch for Fortinet FortiOS and FortiProxy as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.