Attackers exploit Fortinet flaws to deploy Qilin ransomware
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2024-21762 | Out-of-Bounds Write RCE in Fortinet FortiOS and FortiProxy CVE-2024-21762 is a critical (CVSS 9.8) out-of-bounds write (CWE-787) in the SSL VPN functionality of Fortinet FortiOS and FortiProxy, allowing an unauthenticated remote attacker to execute unauthorized code or commands by sending specifically crafted requests to the vulnerable service. No authentication or user interaction is required, and network access to the SSL VPN interface is the only precondition. Organizations running affected FortiOS versions (on FortiGate appliances) or any affected FortiProxy version are exposed, particularly where the SSL VPN is internet-facing. The flaw is actively exploited: it was added to CISA's Known Exploited Vulnerabilities catalog on 2024-02-09 with ransomware use noted, EPSS puts the 30-day exploitation probability at 84.3%, and public scans suggest roughly 150,000 internet-exposed Fortinet devices may be impacted. Do: Upgrade FortiOS and FortiProxy to fixed releases outside the affected ranges per Fortinet's advisory, prioritizing internet-facing devices; as an interim mitigation, disable SSL VPN (or SSL VPN web mode) where it is not required, per vendor and CISA guidance. After patching, check for signs of compromise and rotate credentials, since Fortinet has warned that attackers retained access to FortiGate devices post-patching. The flaw is in CISA KEV with known ransomware use, so treat this as an urgent patching priority. | 9.8 | 84% | KEV ransomware |
| mass≈150,000 internet-exposed FortiGate/FortiProxy devices (public internet-wide scans) | |
| CVE-2024-55591 | Unauthenticated Super-Admin Bypass in Fortinet FortiOS and FortiProxy CVE-2024-55591 is an authentication bypass (CWE-288) in the Node.js websocket module of Fortinet FortiOS and FortiProxy that lets a remote, unauthenticated attacker gain super-admin privileges via crafted websocket requests. It affects FortiOS 7.0.0 through 7.0.16 and FortiProxy 7.0.0 through 7.0.19 and 7.2.0 through 7.2.12, and is trivially triggerable from the network with no user interaction given network access to the management/websocket interface. Successful exploitation gives full super-admin control of the appliance, which attackers can use to pivot, create persistent access, and deploy ransomware. Any organization running the affected FortiOS or FortiProxy versions, especially with admin interfaces reachable from the internet, is affected. Exploitation is confirmed in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2025-01-14, and multiple ransomware crews (reported as Gunra, SuperBlack, and Mora_001) are actively exploiting it. Do: Upgrade all affected systems beyond the vulnerable ranges — FortiOS later than 7.0.16 and FortiProxy later than 7.0.19 / 7.2.12 — following Fortinet's advisory, or apply the vendor's mitigations where upgrades are not possible (per CISA KEV instructions). Restrict access to the admin/websocket interface from the internet, and hunt for unauthorized super-admin accounts and suspicious websocket connections, since ransomware operators are actively exploiting this flaw. Verify device versions and audit logs for signs of compromise before and after patching. | 9.8 | 98% | KEV ransomware |
| large≈48,000+ internet-exposed Fortinet devices per public scans, out of an installed base in the hundreds of thousands | |
| CVE-2025-24472 | Authentication Bypass in Fortinet FortiOS and FortiProxy Grants Super-Admin Access CVE-2025-24472 is an authentication bypass (CWE-288) in the Fortinet Security Fabric of FortiOS and FortiProxy. A remote, unauthenticated attacker who already knows the serial numbers of both the upstream and downstream devices can send crafted CSF proxy requests to gain super-admin privileges on the downstream device; the attack only works where the Security Fabric is enabled, and the need for serial-number knowledge raises attack complexity. An attacker gains full super-admin control of the downstream Fortinet device, which can serve as a foothold for network-wide compromise. Organizations running affected FortiOS 7.0.x or FortiProxy 7.0.x/7.2.x builds with Security Fabric enabled are in scope. The flaw was added to CISA's KEV catalog on 2025-03-18 with known ransomware use, and multiple ransomware groups (including Gunra, SuperBlack, Mora_001 and Qilin operators) have been reported exploiting Fortinet firewall flaws in recent campaigns. Do: Upgrade FortiOS 7.0.x and FortiProxy 7.0.x/7.2.x deployments to the fixed releases listed in the Fortinet PSIRT advisory for CVE-2025-24472, and identify any devices where the Security Fabric is enabled and serial numbers of peer devices may be discoverable. As interim mitigation, restrict or disable Security Fabric (CSF) connectivity toward untrusted peers and limit access to the CSF proxy handling path. Because the flaw is KEV-listed with known ransomware use, federal agencies must apply vendor mitigations per BOD 22-01 or discontinue use, and all defenders should review device logs for unexpected super-admin sessions and anomalous CSF proxy traffic. | 8.1 | 7% | KEV ransomware |
| masshundreds of thousands of deployed Fortinet appliances plausibly affected; the practical subset is those with Security Fabric enabled |
Full article567 words · extracted from securityaffairs.com · click to collapse
Qilin ransomware now exploits Fortinet vulnerabilities to achieve remote code execution on impacted devices.
Threat intelligence firm PRODAFT warned that Qilin ransomware (aka Phantom Mantis) group targeted multiple organizations between May and June 2025 by exploiting multiple FortiGate vulnerabilities, including CVE-2024-21762, and CVE-2024-55591.
“Phantom Mantis recently launched a coordinated intrusion campaign targeting multiple organizations between May and June 2025. Initial access are being achieved by exploiting multiple FortiGate vulnerabilities, including CVE-2024-21762, CVE-2024-55591, and others.” reads the report published by PRODAFT.
— PRODAFT (@PRODAFT) June 6, 2025🚨 Threat actors are actively exploiting Fortigate vulnerabilities (CVE-2024-21762, CVE-2024-55591, and others) to deploy Qilin ransomware.
The attack is fully automated, with only victim selection done manually.
Details in our flash alert on CATALYST: https://t.co/BDjEX2KqqO pic.twitter.com/oRHQzzIph8
The Qilin ransomware group has been active since at least August 2022 but gained attention in June 2024 for attacking Synnovis, a UK governmental service provider for healthcare. The group typically employs “double extortion,” stealing and encrypting victims’ data, then threatening to expose it unless a ransom is paid.
The ransomware group is currently targeting organizations in Spanish-speaking countries through FortiGate vulnerabilities, but experts warn it could expand globally. Despite the regional focus, the group appears to choose victims opportunistically rather than by region or sector.
In February 2024, Fortinet warned that the critical remote code execution vulnerability CVE-2024-21762 (CVSS score 9.6) in FortiOS SSL VPN was actively exploited in attacks in the wild. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added this vulnerability to its Known Exploited Vulnerabilities (KEV) catalog.
In March 2025, researchers at Forescout Research – Vedere Labs reported that between January and March, threat actors exploited two Fortinet vulnerabilities to deploy the SuperBlack ransomware. The experts attribute the attacks to a threat actor named “Mora_001” which uses Russian-language artifacts and exhibits a unique operational signature. The experts speculate Mora_001 could be linked to the LockBit ecosystem, reflecting the growing complexity of ransomware operations.
Mora_001 used the leaked LockBit builder to create encryptor, tracked by Forescout as SuperBlack ransomware, and removed any LockBit’s branding.
However, Mora_001 is tracked as an independent threat actor, it exhibits consistent post-exploitation tactics, including identical usernames across victims, overlapping IPs, and rapid ransomware deployment within 48 hours. It is interesting to note that the ransom note shares a TOX ID with LockBit, suggesting a potential affiliation. However, its structured playbook and unique operational patterns distinguish it as a separate entity capable of independent intrusions.
CISA confirmed that the flaw CVE-2025-24472 is known to be used in ransomware campaigns.
The flaw CVE-2024-55591 is 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. The flaw could allow a remote attacker to gain super-admin privileges via crafted requests to Node.js websocket module.
“An Authentication Bypass Using an Alternate Path or Channel vulnerability [CWE-288] affecting FortiOS and FortiProxy may allow a remote attacker to gain super-admin privileges via crafted requests to Node.js websocket module or via crafted CSF proxy requests.” reads the advisory. “Please note that reports show this is being exploited in the wild.”
Threat actors exploit the flaws to create rogue admin or local users, modify firewall policies, and access SSL VPNs to gain access to internal networks.
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