Attack Chain

1. Reconnaissance & Vulnerability Identification: An attacker identifies publicly exposed and unpatched Mitel MiCollab or Openscape UC servers within a target organization's network perimeter.
2. Initial Exploitation (RCE): The attacker crafts and sends a specially malformed HTTP request or input payload designed to trigger an arbitrary code execution vulnerability on the vulnerable server.
3. Initial Exploitation (XSS): Alternatively or in parallel, the attacker exploits an indirect remote code injection (XSS) vulnerability by injecting malicious client-side script into a data field or application response.
4. Arbitrary Code Execution: The vulnerable Mitel server processes the malicious input, leading to the execution of attacker-controlled code with the privileges of the affected service or system.
5. Client-Side Script Execution: If the XSS vulnerability is successfully exploited, the injected script executes within the web browser of any legitimate user who subsequently accesses the compromised application.
6. Impact (RCE): Successful RCE provides the attacker with unauthorized control over the affected Mitel server, enabling actions such as deploying malware, establishing persistence, exfiltrating sensitive data, or pivoting to other systems.
7. Impact (XSS): Successful XSS allows the attacker to compromise user sessions, steal credentials, deface web content, or perform other client-side malicious actions, affecting users interacting with the vulnerable application.

Impact

The successful exploitation of these vulnerabilities can lead to severe consequences for organizations utilizing the affected Mitel products. Remote Code Execution allows attackers to gain complete control over the compromised server, potentially leading to unauthorized access to sensitive data, system disruption, installation of backdoors, or the deployment of ransomware. Cross-Site Scripting (XSS) attacks can compromise user accounts, steal session cookies, deface websites, or launch phishing attacks against users interacting with the vulnerable application. Organizations in various sectors relying on these communication platforms for their daily operations are at risk of significant operational disruption and data breaches.

Recommendation

• Refer to the Mitel security advisories and promptly apply the recommended patches to all affected MiCollab and Openscape UC instances.
• Block network connections to indicators of compromise from the iocs table at the network perimeter.
• Regularly review web server logs for unusual requests or patterns associated with RCE or XSS exploitation attempts, including webserver category logs for unusual cs-uri-stem or cs-uri-query values.