Thousands of Qlik Sense Servers Open to Cactus Ransomware

Nearly five months after security researchers warned of the Cactus ransomware group leveraging a set of three vulnerabilities in Qlik Sense data analytics and business intelligence (BI) platform, many organizations remain dangerously vulnerable to the threat.

Qlik disclosed the vulnerabilities in August and September. The company's August disclosure involved two bugs in multiple versions of Qlik Sense Enterprise for Windows tracked as CVE-2023-41266 and CVE-2023-41265. The vulnerabilities, when chained, give a remote, unauthenticated attacker a way to execute arbitrary code on affected systems. In September, Qlik disclosed CVE-2023-48365, which turned out to be a bypass of Qlik's fix for the previous two flaws from August.

Gartner has ranked Qlik as one of the top data visualization and BI vendors in the market.

Continued Exploitation of Qlik Security Bugs

Two months later, Arctic Wolf reported observing operators of Cactus ransomware exploiting the three vulnerabilities to gain an initial foothold in target environments. At the time, the security vendor said it was responding to multiple instances of customers encountering attacks via the Qlik Sense vulnerabilities and warned of the Cactus group campaign as being rapidly developing.

Even so, many organization appear not to have received the memo. A scan by researchers at Fox-IT on April 17 uncovered a total of 5,205 Internet-accessible Qlik Sense servers, of which 3,143 servers were still vulnerable to Cactus group's exploits. Of that number, 396 servers appeared to be located in the US. Other countries with a relatively high number of vulnerable Qlik Sense servers include Italy with 280, Brazil with 244 and Netherlands and Germany with 241 and 175 respectively.

Fox-IT is among a group of security organizations in the Netherlands — including the Dutch Institute for Vulnerability Disclosure (DIVD) — working collaboratively under the aegis of an effort called Project Melissa, to disrupt Cactus group operations.

Upon discovering the vulnerable servers, Fox-IT relayed its fingerprints and scan data to DIVD, which then began contacting administrators of the vulnerable Qlik Sense servers about their organization's exposure to potential Cactus ransomware attacks. In some instances, DIVD sent the notifications out directly to potential victims while in others the organization attempted to relay the information to them via their respective country computer emergency response teams.

Security Orgs Are Notifying Potential Cactus Ransomware Victims

The ShadowServer Foundation is also reaching out to at-risk organizations. In a critical alert this week, the nonprofit threat intelligence service described the situation as one where a failure to remediate could leave organizations at a very high likelihood of compromise.

"If you receive an alert from us on a vulnerable instance detected in your network or constituency, please also assume compromise of your instance and possibly your network," ShadowServer said. "Compromised instances are determined remotely by checking for the presence of files with .ttf or .woff file extension."

Fox-IT said it had identified at least 122 Qlik Sense instances as likely compromised via the three vulnerabilities. Forty-nine of them were in the US; 13 in Spain; 11 in Italy; and the rest scattered across 17 other countries. "When the indicator of compromise artefact is present on a remote Qlik Sense server, it can imply various scenarios," Fox-IT said. It could for instance, suggest that the attackers executed code remotely on the server, or it could simply be an artifact from a previous security incident.

"It's crucial to understand that 'already compromised' can mean that either the ransomware has been deployed and the initial access artifacts left behind were not removed, or the system remains compromised and is potentially poised for a future ransomware attack," Fox-IT said.