Security researchers at Synack have detailed a critical vulnerability in Mitel MiCollab that could allow unauthenticated attackers to execute commands with root privileges.
The vulnerability, identified as MTLVULN-1667, received a maximum CVSS score of 10.0 and was patched by Mitel on June 17, 2026. Synack researcher Mustafa Can Ipekci uncovered the issue while investigating what initially appeared to be a server-side request forgery vulnerability.
Instead, the research revealed an unusual command injection path involving TLS certificates.
Certificate Data Created An Attack Path
The vulnerability centered on how MiCollab processed the Common Name field contained within a TLS certificate.
During testing, Ipekci identified unauthenticated SOAP endpoints that could cause the MiCollab appliance to connect to an attacker-controlled server.
When the appliance made that connection, it retrieved the server’s TLS certificate. An attacker could insert command syntax into the certificate’s Common Name field, creating a path for malicious input to reach the operating system.
The unusual part of the attack is that the malicious command does not need to be contained in the initial request sent to MiCollab.
Instead, it arrives later when the system establishes the outbound TLS connection.
Commands Could Execute Before Certificate Rejection
Synack found that commands embedded within the Common Name could execute even when MiCollab ultimately determined that the certificate was invalid.
That allowed the researchers to move from an unauthenticated request to root-level command execution.
The vulnerability is particularly significant because exploitation did not require an authenticated account or previous access to the MiCollab environment.
Security Automation Faces A Detection Challenge
The attack also demonstrates a challenge for automated security systems.
Many security tools inspect inbound requests for recognizable malicious parameters, commands or payloads. In this case, the dangerous input can arrive separately through a TLS certificate after the target initiates another connection.
That creates an attack chain that may be harder for traditional request-based security controls to identify.
Organizations using affected MiCollab environments should ensure Mitel’s security updates have been applied and review network monitoring policies for unexpected outbound connections from communications infrastructure.
The vulnerability highlights a broader issue for automated security operations: as enterprise systems make more machine-to-machine connections, security monitoring increasingly needs visibility into the full sequence of automated interactions rather than just the initial request.