TrueConf Server sandbox escape lets attacker take over server
TrueConf Server, self-hosted video conferencing software, has a critical flaw that lets an attacker who is already running code inside its isolated sandbox break out of it. Once out, the attacker can run commands directly on the server that hosts the video calls.
- Severity
- CriticalCVSS 3.1 · 9.0
- Fix
- Fixed in 5.3.9Fix recorded on Aug 26, 2026
- Affected versions
- before 5.3; 5.3 to before 5.3.9; 5.4 to before 5.4.9+1 more
- Weakness
- CWE-94Code Injection
- Exploit likelihood
- 1.8% in 30 daysEPSS, higher than 78% of known flaws
- Affects
- TrueConf Server
- Exploited
- Yes, in the wildListed by CISA
- Added to CISA list
- Aug 20, 2026
- Federal fix deadline
- Sep 3, 2026
How it works
An attacker who can already run a script inside TrueConf Server's isolated code-execution environment sends a specially crafted script that breaks that environment's containment and runs commands on the real server operating system underneath it.
What to do
Check your TrueConf Server version in the admin panel and compare it against the affected ranges 5.3.x through 5.3.9, 5.4.x through 5.4.9, and 5.5.x through 5.5.5. Update to version 5.3.9, 5.4.9, or 5.5.5 (matching your current branch) or a later release, and make sure port 4307/TCP is not reachable from untrusted networks.
Update to outdated TrueConf versions immediately to fix this flaw.
Technical details
TrueConf Server contains a code injection vulnerability that could allow an unauthorized remote attacker with network access via port 4307/TCP to use a specially crafted script to break out of the isolated environment and execute arbitrary code on the host system.
Severity breakdown
- Attack vector Network Requires network access to the vulnerable service
- Attack complexity High Attack depends on conditions outside the attacker's control
- Privileges required None Attacker needs no account or login
- User interaction None No victim action needed
- Scope Changed Impact crosses a security authority boundary
- Confidentiality impact High Sensitive data can be exposed with serious impact
- Integrity impact High Protected data can be changed with serious impact
- Availability impact High The service can stop or suffer serious disruption
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H Open in FIRST.org calculatorReferences
- securelist.com · 120988 Exploit Third Party Advisory
- ics-cert.kaspersky.com · 2026 Third Party Advisory
- cisa.gov · known-exploited-vulnerabilities-catalog US Government Resource