Fortinet patches bug letting attackers takeover servers remotely

Fortinet patches bug letting attackers takeover servers remotely

Fortinet has released security updates to address a command injection vulnerability that can let attackers take complete control of servers running vulnerable FortiWeb web application firewall (WAF) installations.

The security flaw discovered by Rapid7 researcher William Vu impacts is yet to receive a CVE ID, and it impacts Fortinet FortiWeb versions 6.3.11 and earlier.

Successful exploitation allows authenticated attackers to execute arbitrary commands as the root user on the underlying system via the SAML server configuration page.

While attackers must be authenticated to the management interface of the targeted FortiWeb device to abused this bug, they can easily chain with other vulnerabilities such as the CVE-2020-29015 authentication bypass fixed earlier this year.

“An attacker can leverage this vulnerability to take complete control of the affected device, with the highest possible privilege,” Rapid7 explained.

“They might install a persistent shell, crypto mining software, or use the compromised platform to reach into the affected network beyond the DMZ.”

To defend against attacks that would try to exploit this bug, admins are advised to block access to the FortiWeb device’s management interface from untrusted networks (i.e., the Internet).

Such devices should only be reachable via trusted, internal networks or a secure VPN connection to block threat actors’ exploitation attempts.

Disclosure Timeline:

  • June 2021: Issue discovered and validated by William Vu of Rapid7
  • Thu, Jun 10, 2021: Initial disclosure to the vendor via their PSIRT Contact Form
  • Fri, Jun 11, 2021: Acknowledged by the vendor (ticket 132097)
  • Wed, Aug 11, 2021: Followup with the vendor
  • Tue, Aug 17, 2021: Public disclosure

Fortinet appliances are an attractive target

Financially motivated and state-sponsored threat actors have been heavily targeting unpatched Fortinet servers over the years.

For instance, they have abused the CVE-2018-13379 Fortinet SSL VPN vulnerability to compromise Internet-exposed U.S. election support systems, with Fortinet warning customers to patch the flaw in August 2019July 2020November 2020, and again in April 2021.

In November, a threat actor shared a list of one-line CVE-2018-13379 exploits that could’ve been used to steal VPN credentials for approximately 50,000 Fortinet VPN servers, including government entities and banks.

Earlier this year, Fortinet fixed multiple vulnerabilities impacting several of its products. The patched issues include Remote Code Execution (RCE), SQL Injection, and Denial of Service (DoS) bugs in FortiProxy SSL VPN and FortiWeb Web Application Firewall (WAF) products.

In April, the FBI and CISA warned of state-sponsored hacking groups gaining access to Fortinet appliances by exploiting CVE-2018-13379CVE-2020-12812, and CVE-2019-5591 FortiOS vulnerabilities.

Kaspersky also revealed the same month that Fortinet VPNs are being exploited by a new human-operated ransomware strain known as Cring (aka Crypt3r, Vjiszy1lo, Ghost, Phantom) to breach and encrypt industrial sector companies’ networks.

One month later, the FBI issued a flash alert warning of state-sponsored attackers breaching a US municipal government server after compromising a Fortinet FortiGate firewall appliance.

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