CVE-2026-20045: Cisco Unified Communications Manager RCE

CVE-2026-20045 Overview

A critical remote code execution vulnerability exists in multiple Cisco Unified Communications products, including Cisco Unified Communications Manager (Unified CM), Cisco Unified Communications Manager Session Management Edition (Unified CM SME), Cisco Unified Communications Manager IM & Presence Service (Unified CM IM&P), Cisco Unity Connection, and Cisco Webex Calling Dedicated Instance. This vulnerability allows an unauthenticated, remote attacker to execute arbitrary commands on the underlying operating system of an affected device.

The vulnerability stems from improper validation of user-supplied input in HTTP requests. An attacker can exploit this by sending a sequence of crafted HTTP requests to the web-based management interface of an affected device. Successful exploitation allows the attacker to obtain user-level access to the underlying operating system and subsequently elevate privileges to root.

Critical Impact

This vulnerability is actively exploited in the wild and has been added to CISA's Known Exploited Vulnerabilities Catalog. Unauthenticated remote attackers can achieve root-level access on affected Cisco voice infrastructure components through crafted HTTP requests.

Affected Products

• Cisco Unified Communications Manager (Unified CM)
• Cisco Unified Communications Manager Session Management Edition (Unified CM SME)
• Cisco Unified Communications Manager IM & Presence Service (Unified CM IM&P)
• Cisco Unity Connection
• Cisco Webex Calling Dedicated Instance

Discovery Timeline

• 2026-01-21 - CVE-2026-20045 published to NVD
• 2026-01-22 - Last updated in NVD database

Technical Details for CVE-2026-20045

Vulnerability Analysis

This vulnerability is classified as CWE-94 (Improper Control of Generation of Code, also known as Code Injection). The flaw exists in the web-based management interface of affected Cisco Unified Communications products, where user-supplied input in HTTP requests is not properly validated before being processed by the application.

The web-based management interface fails to adequately sanitize specially crafted input, allowing attackers to inject and execute arbitrary commands on the underlying operating system. The attack requires no authentication, making it particularly dangerous for internet-exposed management interfaces.

Cisco has assigned this vulnerability a Security Impact Rating (SIR) of Critical rather than High because successful exploitation allows an attacker to not only gain initial user-level access but also elevate privileges to root, resulting in complete system compromise.

Root Cause

The root cause of this vulnerability is improper validation of user-supplied input within HTTP request handling in the web-based management interface. The application fails to properly sanitize or validate input parameters before using them in operations that interact with the underlying operating system, enabling code injection attacks.

Attack Vector

The attack is conducted remotely over the network without requiring any authentication or user interaction. An attacker exploits this vulnerability by sending a sequence of specially crafted HTTP requests to the web-based management interface of a vulnerable device. The attack chain follows this pattern:

1. The attacker identifies an accessible web-based management interface of a vulnerable Cisco Unified Communications product
2. Crafted HTTP requests containing malicious payloads are sent to the interface
3. Due to improper input validation, the malicious commands are processed and executed on the underlying operating system
4. Initial access is gained at user-level privileges
5. The attacker then leverages additional techniques to escalate privileges to root

The vulnerability mechanism involves improper handling of HTTP request parameters that allows command injection. When specially crafted requests are processed by the web-based management interface, the unsanitized input is passed to system functions that execute commands on the underlying operating system. For detailed technical information, refer to the Cisco Security Advisory.

Detection Methods for CVE-2026-20045

Indicators of Compromise

• Unusual HTTP request patterns targeting the web-based management interface with malformed or encoded parameters
• Unexpected processes spawning from web server processes on affected Cisco Unified Communications systems
• Evidence of privilege escalation attempts or creation of new administrative accounts
• Suspicious outbound network connections from Cisco voice infrastructure components

Detection Strategies

• Implement network intrusion detection rules to identify crafted HTTP requests targeting Cisco Unified Communications management interfaces
• Monitor web server access logs for anomalous request patterns, especially those containing shell metacharacters or encoded payloads
• Deploy endpoint detection on affected systems to identify unauthorized process execution and privilege escalation attempts
• Use SentinelOne Singularity to detect and block command injection attempts and unauthorized code execution on protected endpoints

Monitoring Recommendations

• Enable detailed logging on all Cisco Unified Communications Manager web-based management interfaces
• Configure SIEM alerts for authentication bypass attempts and suspicious administrative actions
• Monitor for unexpected changes to system configurations, user accounts, or scheduled tasks
• Implement network segmentation monitoring to detect lateral movement from compromised voice infrastructure

How to Mitigate CVE-2026-20045

Immediate Actions Required

• Apply Cisco security patches immediately for all affected Unified Communications products
• Restrict access to web-based management interfaces to trusted networks only using firewall rules and ACLs
• Disable unnecessary web-based management interfaces where possible
• Implement network segmentation to isolate voice infrastructure from general network traffic
• Review system logs for evidence of prior exploitation attempts

Patch Information

Cisco has released security updates to address this vulnerability. Administrators should consult the Cisco Security Advisory for specific patch versions and upgrade instructions for each affected product. Due to active exploitation in the wild and inclusion in the CISA Known Exploited Vulnerabilities Catalog, federal agencies and organizations following CISA guidance should prioritize patching according to specified deadlines.

Workarounds

• Implement strict IP-based access control lists (ACLs) to limit management interface access to authorized administrator workstations only
• Deploy a web application firewall (WAF) in front of management interfaces to filter malicious HTTP requests
• Consider using out-of-band management networks that are completely isolated from production traffic
• Enable multi-factor authentication for all administrative access where supported

# Example: Restrict management interface access using firewall rules
# Allow management access only from trusted administrator subnet
iptables -A INPUT -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP

# Example: Verify current access restrictions
show ip access-list | grep management