FBI and CISA are warning of APT actors targeting Fortinet FortiOS servers
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2018-13379 | Unauthenticated Path Traversal in Fortinet FortiOS SSL VPN CVE-2018-13379 is a path traversal flaw (CWE-22) in the Fortinet FortiOS SSL VPN web portal that allows an unauthenticated attacker to download FortiOS system files via specially crafted HTTP resource requests. By traversing directories through crafted requests to the exposed web portal, the attacker can retrieve sensitive files, a technique publicly documented as yielding the SSL VPN session file containing usernames and passwords in plaintext. Any organization running the SSL VPN web portal on a FortiGate appliance is affected, and risk is highest where the portal is directly reachable from the internet. The flaw is confirmed in the wild: it was added to the CISA KEV catalog on 2021-11-03 with known ransomware use, and EPSS assigns it a 100% probability of exploitation within 30 days. No public PoC is listed in the provided data, but credential theft tied to this bug has been widely reused by threat actors. Do: Apply the patched FortiOS release per Fortinet's vendor advisory immediately, as this is a CISA KEV required action; if the fixed version is not known from this data, follow Fortinet's FG-IR-18-384 advisory for the correct upgrade path. Rotate SSL VPN credentials and review VPN access logs for path-traversal requests, since successful exploitation exposes plaintext session credentials, and restrict SSL VPN portal exposure to trusted sources where possible. | 9.8 | 100% | KEV ransomware |
| mass≈500,000 internet-exposed FortiOS SSL VPN portals (Fortinet cited ~480,000 affected devices) | |
| CVE-2019-5591 | Default-Configuration LDAP Impersonation in Fortinet FortiOS CVE-2019-5591 is a default-configuration flaw in Fortinet FortiOS (CWE-306, missing authentication for a critical function): when a FortiGate acts as an LDAP client over SSL/TLS for authentication purposes, the default configuration does not properly authenticate the LDAP server, allowing an unauthenticated attacker on the same subnet to impersonate the LDAP server. The attack requires adjacency (the attacker must be on the same network segment as the device's LDAP traffic) and only works where the device uses LDAP over TLS with the default, non-validating settings. A successful attacker can intercept sensitive authentication information, such as usernames and passwords, exchanged with the LDAP server, with high confidentiality impact but no integrity or availability impact per the CVSS score. Organizations running affected FortiOS releases with LDAP-over-TLS configured are exposed; FortiOS runs on one of the largest firewall/VPN installed bases, though the source data does not state exact affected version ranges or deployment counts. The flaw is listed in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) with known in-the-wild and ransomware use; late-2021 CISA and FBI advisories warned that APT actors were exploiting Fortinet bugs, including this one, for initial access, and no public PoC is known. Do: Upgrade affected FortiGate/FortiOS units to a fixed release (6.2.1+, 6.0.8+, 5.6.10+, or 5.4.12+) per Fortinet's instructions, as required by CISA's KEV listing. If patching is delayed, disable the use of SSL/TLS in the LDAP server configuration or restrict and monitor the network path between the FortiGate and the LDAP server. Inventory which devices use LDAPS for authentication and review authentication logs for signs of server impersonation or credential theft. | 6.5 | 18% | KEV ransomware |
| largetens of thousands of FortiGate deployments plausibly affected (a subset of a very large FortiOS installed base that connects to LDAP over TLS) | |
| CVE-2020-12812 | MFA Bypass via Username Case Change in Fortinet FortiOS SSL VPN Fortinet FortiOS SSL VPN improperly validates the second factor of authentication (FortiToken), allowing a user with valid primary credentials to log in without being prompted for their one-time token. The bypass is triggered by changing the letter case of the username (e.g., typing 'Admin' instead of 'admin'), a case-sensitivity handling flaw (CWE-178) in the authentication logic (CWE-287). An attacker who has stolen, phished, or reused a user's primary credentials can therefore gain full SSL VPN access without the multi-factor protection defenders assume is enforced. Any organization running an affected FortiOS SSL VPN portal with FortiToken two-factor authentication for users is exposed. The flaw is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) with known ransomware use, and EPSS assigns a 49.3% probability of exploitation within 30 days (99th percentile); no public PoC is known. Do: Apply the FortiOS update per Fortinet's advisory, as required by CISA's KEV listing. Until patched, audit SSL VPN logs for successful logins in which no FortiToken second-factor prompt occurred (especially sessions authenticating with altered username case), and consider restricting the SSL VPN portal to trusted source addresses or disabling it temporarily. Any accounts found with second-factor-free VPN logins should have credentials rotated and be checked for follow-on compromise, given known ransomware use. | 9.8 | 49% | KEV ransomware |
| masson the order of hundreds of thousands of internet-exposed FortiOS SSL VPN portals (public scans in 2020-2021 counted roughly 150,000-500,000) | |
| CVE-2020-1472 | Unauthenticated Privilege Escalation (Zerologon) in Microsoft Netlogon Domain Controllers CVE-2020-1472, widely known as "Zerologon," is an elevation-of-privilege flaw in how the Netlogon secure channel is established over the Netlogon Remote Protocol (MS-NRPC) on Microsoft domain controllers. An unauthenticated attacker with network reachability to a domain controller sends specially crafted Netlogon messages to establish a vulnerable secure channel and then runs a specially crafted application on the network to obtain domain administrator access. Successful exploitation yields domain administrator privileges, effectively full compromise of the Active Directory environment, and the flaw is known to be used in ransomware operations. Any organization running affected Windows Server versions (2008 through 20H2) as domain controllers is exposed, along with environments using Netlogon implementations from Samba and distributions or products from Fedora, openSUSE, Canonical (Ubuntu), Debian, Synology, and Oracle. Exploitation is highly active: a public Zerologon PoC/exploit is available, the flaw is on CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03, with known ransomware use), and EPSS estimates a 99.4% probability of exploitation within 30 days. Do: Apply the vendor updates on all domain controllers and other affected systems immediately, following Microsoft's two-phase Netlogon secure channel guidance (the enforcement phase of the phased rollout began in Q1 2021). Audit Netlogon secure-channel connections and event logs for clients still using vulnerable connections before enabling full enforcement, and install updated packages for Samba and other Netlogon implementations from Fedora, openSUSE, Ubuntu, Debian, Synology, and Oracle. Given known ransomware use, prioritize patching any domain controller reachable from user networks, VPNs, or the internet. | 5.5 | 99% | KEV ransomware PoC |
| massmillions of domain controllers worldwide (essentially every Active Directory domain), with hundreds of thousands of domain controllers/RPC endpoints… |
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FBI and CISA published a joint alert to warn of advanced persistent threat (APT) groups targeting Fortinet FortiOS to access networks of multiple organizations.
The Federal Bureau of Investigation (FBI) and the Cybersecurity and Infrastructure Security Agency (CISA) published a joint alert to warn of attacks carried out by APT groups targeting Fortinet FortiOS servers using multiple exploits.
The threat actors are actively exploiting the following vulnerabilities in Fortinet FortiOS:
In March 2021, government experts observed state sponsored hackers scanning the internet for servers vulnerable to the above flaws, the attackers were probing systems on ports 4443, 8443, and 10443. The joint alert also states that attackers scanning also enumerated devices for the CVE-2020-12812 and CVE-2019-5591 flaws.
“In March 2021 the Federal Bureau of Investigation (FBI) and the Cybersecurity and Infrastructure Security Agency (CISA) observed Advanced Persistent Threat (APT) actors scanning devices on ports 4443, 8443, and 10443 for CVE-2018-13379, and enumerated devices for CVE-2020-12812 and CVE-2019-5591. It is likely that the APT actors are scanning for these vulnerabilities to gain access to multiple government, commercial, and technology services networks” reads the joint advisory published by FBI and CISA.
Attackers were exploiting the flaw in the attempt to access multiple government, commercial, and technology services networks.
The agencies warn APT actors may be using any or all of these CVEs to gain access to networks across multiple critical infrastructure sectors. Once gained access to the target networks, attackers can establish a foothold for future malicious activities.
“The APT actors may be using any or all of these CVEs to gain access to networks across multiple critical infrastructure sectors to gain access to key networks as pre-positioning for follow-on data exfiltration or data encryption attacks,” continues the advisory. “APT actors may use other CVEs or common exploitation techniques—such as spearphishing—to gain access to critical infrastructure networks to pre-position for follow-on attacks.”
The alert also includes mitigation measures to secure systems from ongoing state-sponsored attacks exploiting the above issues:
• Immediately patch CVEs 2018-13379, 2020-12812, and 2019-5591.
• If FortiOS is not used by your organization, add key artifact files used by FortiOS to your organization’s execution deny list. Any attempts to install or run this program and its associated files should be prevented.
• Regularly back up data, air gap, and password protect backup copies offline. Ensure copies of critical data are not accessible for modification or deletion from the primary system where the data resides.
• Implement network segmentation.
• Require administrator credentials to install software.
• Implement a recovery plan to restore sensitive or proprietary data from a physically separate, segmented, secure location (e.g., hard drive, storage device, the cloud).
• Install updates/patch operating systems, software, and firmware as soon as updates/patches are released.
• Use multifactor authentication where possible.
• Regularly change passwords to network systems and accounts, and avoid reusing passwords for different accounts. Implement the shortest acceptable timeframe for password changes.
• Disable unused remote access/Remote Desktop Protocol (RDP) ports and monitor remote access/RDP logs.
• Audit user accounts with administrative privileges and configure access controls with least privilege in mind.
• Install and regularly update antivirus and anti-malware software on all hosts.
• Consider adding an email banner to emails received from outside your organization.
• Disable hyperlinks in received emails.
• Focus on awareness and training. Provide users with training on information security principles and techniques, particularly on recognizing and avoiding phishing emails.
This isn’t the first time that the FBI and CISA have released a joint security advisory on attacks exploiting vulnerabilities in Fortinet systems. In October, 2020, the US agencies warned that APT actors had been chaining vulnerabilities in VPN products (Fortinet, Pulse Secure) and with Windows ZeroLogon in attacks aimed at federal and state, local, tribal, and territorial (SLTT) government networks, the agencies also reported attacks against non-government networks.
CISA and FBI have observed attacks carried out by APT actors that combined two the CVE-2018-13379 and CVE-2020-1472 flaws.
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