Security researchers have released a proof-of-concept (PoC) exploit for a critical vulnerability in Fortinet's FortiClient Enterprise Management Server (EMS) software, which is now actively exploited in attacks.

Tracked as CVE-2023-48788, this security flaw is an SQL injection in the DB2 Administration Server (DAS) component discovered and reported by the UK's National Cyber Security Centre (NCSC).

It impacts FortiClient EMS versions 7.0 (7.0.1 through 7.0.10) and 7.2 (7.2.0 through 7.2.2), and it enables unauthenticated threat actors to gain remote code execution (RCE) with SYSTEM privileges on unpatched servers in low-complexity attacks that don't require user interaction. 

"An improper neutralization of special elements used in an SQL Command ('SQL Injection') vulnerability [CWE-89] in FortiClientEMS may allow an unauthenticated attacker to execute unauthorized code or commands via specifically crafted requests," Fortinet explains in a security advisory released last week.

While the company didn't initially mention that CVE-2023-48788 was being used in attacks, it has since silently updated the advisory to say that the "vulnerability is exploited in the wild."

On Thursday, one week after Fortinet released security updates to address the security flaw, security researchers with Horizon3's Attack Team published a technical analysis and shared a proof-of-concept (PoC) exploit that helps confirm if a system is vulnerable without providing remote code execution capabilities.

Those who want to use Horizon3's exploit code in RCE attacks must modify the PoC to use the Microsoft SQL Server xp_cmdshell procedure to spawn a Windows command shell for code execution.

"To turn this SQL injection vulnerability into remote code execution we used the built-in xp_cmdshell functionality of Microsoft SQL Server," Horizon3 vulnerability researcher James Horseman said.

"Initially, the database was not configured to run the xp_cmdshell command, however it was trivially enabled with a few other SQL statements."

Shodan currently tracks over 440 FortiClient Enterprise Management Server (EMS) servers exposed online, while the Shadowserver threat monitoring service found more than 300, most of them in the United States.

In February, Fortinet patched another critical RCE bug (CVE-2024-21762) in the FortiOS operating system and FortiProxy secure web proxy, saying it was "potentially being exploited in the wild."

However, the very next day, CISA confirmed that the CVE-2024-21762 bug was being actively exploited and directed federal agencies to secure their FortiOS and FortiProxy devices within seven days.

It's also worth noting that Fortinet security vulnerabilities are frequently used to gain unauthorized access to corporate networks for ransomware attacks and cyber espionage campaigns, often using zero-day exploits.