Microsoft has linked recent attacks on PaperCut servers to ransomware operations by Clop and LockBit, which exploited vulnerabilities to steal corporate data. In March 2023, the print management solutions provider PaperCut fixed two vulnerabilities, CVE-2023-27350 (CVSS 9.8 out of 10) and CVE-2023-27351 (CVSS 8.2 out of 10). These vulnerabilities allowed attackers to bypass authentication and execute arbitrary code on compromised PaperCut servers with SYSTEM privileges, as well as extract usernames, full names, email addresses, and other sensitive data.
In mid-April, it became known that hackers were already exploiting these vulnerabilities, and a proof-of-concept exploit for the most dangerous of them was released to the public. Microsoft Threat Intelligence experts now report that Clop and LockBit ransomware are behind these attacks on PaperCut servers, using the vulnerabilities to steal corporate data.
According to the researchers, hackers have been using the vulnerabilities in PaperCut since April 13, 2023, and with their help they gain access to corporate networks. After gaining access, the attackers deploy the TrueBot malware in the system, which is associated with Clop extortionate operations, as well as the Cobalt Strike “beacon”, which is used to traverse the victim’s network sideways and steal data using the MegaSync file-sharing application. Microsoft states that some of the incidents ended with LockBit ransomware attacks, but it is not clear if these attacks started before or after the exploits were published.
Microsoft urges all administrators to install the available patches as soon as possible, as other attackers are likely to soon take advantage of the vulnerabilities. For example, PaperCut MF and NG users are highly recommended to upgrade to versions 20.1.7, 21.2.11 and 22.0.9.
