About Remote Code Execution - TrueConf Server (CVE-2026-72529, CVE-2026-72530) vulnerability. TrueConf Server is a Russian on-premises corporate messaging and UltraHD video conferencing platform. The attack chain consists of two critical vulnerabilities. The first vulnerability, CVE-2026-72529, is caused by missing authentication for a critical function (CWE-306) and allows an unauthenticated remote attacker with network access to TCP port 4307 (open by default, according to TrueConf documentation) to invoke an undocumented TrueConf Server function and execute an arbitrary script within an isolated environment ("sandbox") where potentially dangerous libraries are unavailable. The second vulnerability, CVE-2026-72530, allows an attacker to perform code injection (CWE-94), escape the isolated environment, and execute arbitrary code on the host operating system with the highest privileges. Among other things, an attacker can delete TrueConf event log entries associated with exploitation activity.

⚙️ Security fixes for these vulnerabilities were released on June 18, 2026. The affected versions are 5.3.x below 5.3.9, 5.4.x below 5.4.9, 5.5.x below 5.5.5, as well as the 5.2 branch and earlier versions (upgrading legacy versions requires contacting technical support). Re-registration of the server is not required when upgrading within the 5.3-5.5 branches. However, the vendor strongly recommends creating a backup before installing the update. If an immediate upgrade is not possible, access to TCP port 4307 should be restricted to trusted networks.

👾 Kaspersky ICS CERT experts have disclosed details of the vulnerability exploitation chain in a post published on August 12. Since July 2026, threat actors have been exploiting CVE-2026-72529 and CVE-2026-72530 in attacks targeting Russian organizations. The attackers first gained network access to TrueConf Server through TCP port 4307 and used CVE-2026-72529 to execute a script within the sandbox. They then exploited CVE-2026-72530 to escape the sandbox and execute code with NT AUTHORITY\SYSTEM privileges. This enabled them to replace one of the TrueConf Server files with a web shell of their own. The attackers then used the web shell to gather information about the organization's IT infrastructure, gain privileged access to the TrueConf Server database, and replace legitimate TrueConf Client installers with malicious versions containing the PhantomCore malware. Users were subsequently prompted to download what appeared to be a new version of the TrueConf Client, which was in fact malicious.

IMPORTANT: Even if your organization does not use TrueConf, your employees may have connected to compromised TrueConf servers used by contractors or business partners to participate in online conferences. In doing so, they may have inadvertently installed a malicious version of the TrueConf client on their workstations.

The PhantomCore malware, associated with the Head Mare APT group, launches automatically when the system starts and allows attackers to execute arbitrary commands, effectively giving them full control over the compromised host. Kaspersky researchers also identified a new backdoor used in the attacks, which they named PhantomGraph. Both vulnerabilities, CVE-2026-72529 and CVE-2026-72530, were added to the CISA KEV on August 20, 2026.

🛠 A public exploit for CVE-2026-72530 was published on GitHub on August 26. So far, no public exploit for the complete CVE-2026-72529/CVE-2026-72530 exploitation chain has been observed, despite the corresponding flags in the BDU FSTEC vulnerability database.

🌐 TrueConf Server is widely used both in Russia and internationally, including by government agencies, as well as organizations in the financial, industrial, healthcare, and education sectors.