CVE-2024-55550

What it actually does

CVE-2024-55550 is an authenticated path traversal/local file read flaw in Mitel MiCollab through 9.8 SP2. An attacker who already has administrative privileges can submit insufficiently sanitized input that causes the application to read local files or resources reachable within the administrative access boundary. The vendor describes the disclosure as limited to non-sensitive system information; the flaw does not provide file write, direct privilege escalation, or code execution by itself. However, because it is listed in CISA KEV, has observed in-the-wild exploitation, and is associated with ransomware campaign activity, organizations should treat it as a real exploitation risk, especially where MiCollab administrative access is exposed or credentials may already be compromised.

Why it matters to the business

The direct impact is information disclosure from a business communications platform, but the operational risk is higher when combined with stolen administrator credentials or other vulnerabilities. Attackers may use exposed system information for reconnaissance, follow-on exploitation, persistence planning, or ransomware intrusion staging. Because this vulnerability is in CISA KEV, has a CISA remediation deadline of 2025-01-28, and is associated with ransomware activity, delayed remediation can increase regulatory, incident-response, outage, and communications-disruption risk for organizations relying on Mitel MiCollab.

How an attack unfolds

An attacker first obtains valid Mitel MiCollab administrative access, commonly through credential theft, phishing, password reuse, exposed management interfaces, or prior compromise. After authenticating, the attacker identifies an administrative function that accepts a file, path, resource, or similar parameter and submits crafted path traversal input such as dot-dot-slash sequences or encoded traversal variants. Because input sanitization is insufficient, the application resolves the attacker-controlled path and returns local system information that should not have been accessible through the intended interface. The attacker may then use the disclosed information to map the appliance, identify software versions, locate configuration details, or support additional attacks. In ransomware-linked activity, this type of bug is most likely used as part of a broader intrusion chain rather than as a standalone compromise mechanism.

How to fix it

Upgrade Mitel MiCollab to a vendor-fixed release newer than the affected range of through 9.8 SP2, following Mitel’s official advisory and upgrade path. If an immediate upgrade is not possible, restrict MiCollab administrative access to trusted management networks or VPN-only access, enforce MFA for administrators, remove unnecessary admin accounts, rotate administrator credentials, and monitor for path traversal attempts. Because the issue is KEV-listed and associated with ransomware campaigns, treat patching as urgent even though the CVSS score is low. Also review whether MiCollab is internet-accessible and disable or firewall administrative endpoints wherever possible.

How to confirm the fix worked

Confirm the installed Mitel MiCollab version is no longer within the affected range of through 9.8 SP2 and matches a vendor-fixed build from Mitel. Validate that administrative interfaces are not publicly reachable unless explicitly required and are protected by network controls and MFA. Review administrative application logs and reverse proxy/WAF logs for traversal payloads before and after remediation. If vulnerability scanners or vendor-provided checks are available, run authenticated version detection rather than relying only on banner checks. A successful fix should reject or normalize traversal input and should not return local file contents or system resources outside the intended administrative function.

Typical attack path

1. Obtain valid administrative credentials for a Mitel MiCollab instance.
2. Authenticate to the MiCollab administrative interface or API.
3. Identify a vulnerable administrative function that accepts a file path or resource identifier.
4. Submit path traversal payloads using sequences such as ../ or encoded equivalents.
5. Read returned local system information available within the administrative access boundary.
6. Use the disclosed information for reconnaissance, targeting, lateral movement planning, or chaining with other vulnerabilities.
7. Cover tracks by minimizing request volume or blending activity with legitimate administrator sessions.

How to detect it

Hunt for evidence of authenticated administrator sessions followed by path traversal-style requests. Relevant log sources include Mitel MiCollab application/admin logs, web access logs, reverse proxy logs, WAF logs, VPN logs, identity provider logs, and firewall logs for administrative access. Look for requests containing dot-dot-slash traversal, URL-encoded traversal, double-encoded traversal, Windows-style traversal, or attempts to read common local files. Correlate suspicious requests with successful administrator logins, especially from new IP addresses, anonymization infrastructure, unusual geographies, off-hours activity, or accounts that do not normally administer MiCollab. Because exploitation requires admin privilege, also investigate credential compromise indicators such as MFA fatigue, new admin sessions after password-spray activity, new administrator accounts, changed authentication settings, or unexpected configuration exports. For ransomware-related concerns, extend the hunt to post-exploitation behavior including network scanning, archive creation, unusual outbound transfers, and authentication attempts from the MiCollab server to other internal systems.

• ../
• ..\\
• %2e%2e%2f
• %2e%2e/
• ..%2f
• %252e%252e%252f
• %2e%2e%5c
• ..%5c
• /etc/passwd
• /etc/hosts
• /etc/hostname
• /etc/issue
• /proc/version
• /proc/self/environ
• C:\\Windows\\win.ini
• C:\\Windows\\System32\\drivers\\etc\\hosts

What your security team should do

• Prioritize remediation immediately because the vulnerability is CISA KEV-listed, has in-the-wild exploitation, and is associated with ransomware activity.
• Upgrade Mitel MiCollab through 9.8 SP2 systems to a vendor-fixed release according to Mitel guidance.
• Restrict MiCollab administrative access to trusted networks, VPN, or dedicated management segments; remove public exposure where possible.
• Enforce MFA and strong credential hygiene for all MiCollab administrative accounts, and rotate admin credentials if exposure or suspicious activity is suspected.
• Hunt historical logs for authenticated admin requests containing traversal sequences, URL-encoded traversal, or attempts to read local system files.
• Review administrator login history for unusual source IPs, impossible travel, new devices, off-hours access, or excessive failed login attempts.
• If suspicious exploitation is found, collect appliance/application logs, proxy logs, authentication logs, and endpoint/network telemetry before containment actions overwrite evidence.
• Assess for chained activity, including credential dumping, lateral movement, new accounts, configuration exports, or ransomware precursor behavior.