CVE-2026-20045 is a recently discovered, critical vulnerability impacting several major Cisco Unified Communications products, including:

Cisco Webex Calling Dedicated Instance

This vulnerability has the potential to let an unauthenticated, remote attacker execute arbitrary commands on the affected device's underlying operating system. More alarmingly, a successful attacker could escalate privileges from user to root, fully compromising the system.

Cisco considers this vulnerability "Critical" in real-world impact, even if its CVSS score suggests a slightly lower severity.

How Does CVE-2026-20045 Work?

The vulnerability arises from improper validation of user-supplied input in HTTP requests. Attackers can exploit this using a carefully crafted HTTP request targeting the web-based management interfaces of the affected devices.

Crafted HTTP Request:

An attacker sends a malicious HTTP request to the management interface, embedding commands within certain parameters or fields.

Command Execution:

The vulnerable server processes the malicious input, allowing execution of commands as a regular user on the operating system.

Privilege Escalation:

With user-level shell access, the attacker can further exploit the environment (e.g., via known privilege escalation vectors or insecure setuid binaries) to gain root access.

A Simple Proof-of-Concept (PoC)

Below is a simplified example of how a remote, unauthenticated attacker might trigger this flaw.

import requests

# Replace with your target device's IP/hostname
target = "https://vulnerable-cisco.example.com";

# Malicious payload
# Assume 'cmd' parameter is not properly sanitized
malicious_param = " ; id ; uname -a ; "

# Make the crafted HTTP request
response = requests.get(
    f"{target}/management_interface.cgi?cmd={malicious_param}",
    verify=False
)

print("Server response:")
print(response.text)

Note:
This is an illustrative generic example. The real vulnerable endpoints and parameter names may vary and can be found by analyzing Cisco’s advisories or using tools like BurpSuite/ZAP to inspect network traffic.

Potential Impact

- Remote Root Compromise: Once root, attackers gain complete control (install malware, exfiltrate data, intercept communications).
- Lateral Movement: If the Unified Communications appliance is integrated with broader enterprise infrastructure, attackers can leverage this foothold for further attacks.
- Persistence: Attackers may disable security logging, create hidden user accounts, or plant persistent backdoors.

Cisco has released software updates that address this vulnerability.

Cisco Security Advisory for CVE-2026-20045

References & Further Reading

- Cisco Security Advisory: CVE-2026-20045
- NVD - CVE-2026-20045 (when published)
- Cisco Product Security Incident Response Team

Final Thoughts

CVE-2026-20045 underscores the critical importance of input validation and restricting administrative interfaces to authorized personnel. All organizations relying on affected Cisco Unified Communications products should patch immediately and review their incident response plans.

If you suspect your environment is affected, contact Cisco support or your security team right away.

*(This article is an exclusive overview based on public disclosures and cybersecurity best practices.)*

Timeline

Published on: 01/21/2026 16:26:20 UTC
Last modified on: 01/22/2026 14:28:35 UTC