Threat Actors Target Qlik Sense Servers with Reverse Shells and Stage ActiveMQ and Veeam Exploits

Cybersecurity researchers at Cynet have detected threat actors attempting to compromise Qlik Sense servers by deploying PowerShell reverse shells in multiple environments during October 2026. The activity shows overlap with a 2023 campaign attributed to the CACTUS ransomware operation that exploited newly disclosed vulnerabilities in Qlik Sense Enterprise for Windows. Although the exact entry vector remains unknown, the commands were executed under scheduler.exe and attempted to establish persistence through additional payloads including a Windows Go reverse shell. The infrastructure also hosted exploits for Apache ActiveMQ CVE-2023-46604 and a modified Veeam toolchain targeting CVE-2024-40711, suggesting preparation for wider attacks. Earlier intrusions linked to CACTUS involved deployment of ManageEngine UEMS, AnyDesk, and Plink after initial access via the Qlik flaws. Cynet blocked the reverse shell attempts but confirmed the backdoor's use for reconnaissance and persistence mechanisms such as scheduled tasks and OpenSSH installation.

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Threat actors have been observed targeting Qlik Sense servers in an attempt to deliver PowerShell reverse shell commands against multiple environments in October 2026. Cynet's CyOps and Research teams identified the suspicious activity within a narrow window of just over three minutes against several E.U.-based customers.

The activity shares overlap with a November 2023 campaign documented by Arctic Wolf, in which threat actors linked to the CACTUS ransomware operation weaponized then-newly-disclosed flaws in Qlik Sense to obtain initial access. The vulnerabilities, patched by Qlik in August and September 2023, include:

  • CVE-2023-41265 (CVSS 9.6) – An HTTP tunneling vulnerability leading to privilege escalation.
  • CVE-2023-41266 (CVSS 8.2) – A path traversal vulnerability allowing unauthenticated remote attackers to generate anonymous sessions.
  • CVE-2023-48365 (CVSS 9.6, aka DoubleQlik) – An unauthenticated remote code execution flaw stemming from improper HTTP header validation; it is an incomplete fix for CVE-2023-41265.

In the 2023 campaign, actors deployed ManageEngine Unified Endpoint Management and Security (UEMS), AnyDesk, and Plink for persistence and remote control. The latest activity involves a PowerShell one-line reverse shell connecting to 45.115.26[.]23 on port 4455. Although blocked, testing showed the channel enables reconnaissance and delivery of a Windows Go reverse shell connecting to port 4456.

The backdoor searches for Apache ActiveMQ processes and, on Linux, collects system information while reading /etc/shadow and /etc/passwd. A second variant installs OpenSSH, creates a scheduled task named WinUpdCheck, and writes a reverse shell to C:\ProgramData\ssh\winc.ps1. The exposed directory at 45.115.26[.]23:8012 contains a custom Go backdoor, SSH persistence scripts, an Apache ActiveMQ exploit for CVE-2023-46604, and a modified Veeam toolchain for CVE-2024-40711.

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