Vulnerabilities

TrueConf Server contains a code injection flaw (CWE-94) that allows a remote, unauthenticated attacker with network access to TCP port 4307 to send a specially crafted script that breaks out of the server's isolated environment and executes arbitrary code on the underlying host. The flaw affects TrueConf Server 5.3.X through 5.3.9, 5.4.X through 5.4.9, 5.5.X through 5.5.5, and earlier releases. A successful attack yields full code execution on the host system, not just the conferencing application, although the critical CVSS 4.0 score of 9.5 includes high attack complexity and attack-requirements factors. Organizations running self-hosted TrueConf video conferencing servers, especially those with port 4307 exposed to untrusted networks, are in scope. Exploitation is confirmed in the wild: CISA added the flaw to the Known Exploited Vulnerabilities catalog on 2026-08-20, a public PoC exists, and Kaspersky's Securelist reports the Head Mare threat actor has actively targeted TrueConf Server to deploy PhantomCore malware.

Do: Upgrade TrueConf Server to a fixed release beyond the affected ranges (later than 5.5.5, per vendor instructions) as the primary remediation. Until patched, restrict access to TCP port 4307 so it is not reachable from untrusted networks and review server logs for signs of exploitation. U.S. federal agencies must apply these mitigations in accordance with BOD 26-04 following the KEV listing (added 2026-08-20), or discontinue use of the product if mitigations are unavailable.