CVE-2025-20309 affects Cisco Unified CM

🔎 Vulnerability Overview

CVE ID: CVE-2025-20309
Severity: Critical (CVSS v3.1 Score: 10.0)
Discovered in: Cisco Unified Communications Manager (Unified CM) and Session Management Edition (SME)
Type: Hardcoded credential / Authentication bypass
Attack Vector: Remote, unauthenticated access over SSH
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Exploitability: High (can be exploited immediately if network access is possible)

🧠 Root Cause & Technical Details

Cisco shipped certain Engineering Special (ES) builds of Unified CM 15.x with a hardcoded SSH account that has root privileges.
This root account was introduced during internal development/testing and mistakenly left enabled in production builds ranging from: 15.0.1.13010-1 through 15.0.1.13017-1
The username and password were static and cannot be removed or modified by administrators, making the system inherently insecure.
A remote attacker who gains network access to the SSH port (default: 22) can log in using the embedded credentials and execute arbitrary commands with full system control.

🛑 Impact

Full root-level compromise of the affected Unified CM systems.
Complete loss of confidentiality, integrity, and availability (CIA).
Potential to use the system as a pivot point to launch further attacks inside corporate VoIP or telephony infrastructure.
May violate compliance requirements (e.g., PCI DSS, HIPAA) due to the presence of unauthorized backdoor access.

🧩 Affected Versions

Cisco Unified CM 15.0.1.13010-1 to 15.0.1.13017-1

Unified CM SME Same as above

🛠️ Remediation Guidance

🔧 Fix Options

Cisco recommends immediate upgrade or hot patching using either of the following:

Upgrade to Unified CM 15SU3, which completely removes the hardcoded credentials.
Apply patch CSCwp27755 if an upgrade is not immediately feasible.

📌 Note: Cisco has confirmed that no other versions outside the listed ES builds are affected.

🔍 Detection & Forensics

🧾 Log Review

Inspect the following log file on affected systems: /var/log/active/syslog/secure
Search for unauthorized logins or attempts by the root account over SSH.
Indicators of compromise (IoCs) may include:
- SSH login events with no corresponding user activity
- Unscheduled configuration changes or CLI command logs
- Logins from unknown external IPs

🧰 Mitigation Steps

If you cannot patch immediately, implement the following mitigations to reduce risk exposure:

Restrict SSH Access
- Use ACLs or firewall rules to restrict port 22 access to trusted IPs only.
- Isolate the Unified CM system to a management VLAN or jump host setup.
Monitor for Abuse
- Deploy SIEM alerts for unexpected SSH access.
- Enable logging and alerting for system-level changes.
Network Segmentation
- Ensure Unified CM is not internet-facing.
- Apply zero trust principles around VoIP infrastructure access.

🧠 Strategic Consideration

This is the latest in a growing series of hardcoded credential issues in enterprise products:

Similar flaws were previously discovered in Cisco IOS XE, WAAS, and DNA Center.
Hardcoded backdoors violate secure development lifecycle (SDL) best practices and erode trust in vendor supply chains.

Organizations should:

Establish a regular patch cycle for VoIP and UC systems.
Demand security transparency from vendors, especially for Engineering Special builds.
Perform pre-deployment vulnerability scans even for vendor-trusted images.

✅ Final Recommendation

CVE-2025-20309 is a critical security threat that enables complete system takeover with no authentication or user interaction. Organizations using affected Cisco Unified CM versions must: