Cisco Unified CM Flaw Exploited After PoC Reveals File-Write Path to Root

Summary

Threat actors are actively exploiting a critical vulnerability in Cisco Unified Communications Manager (Unified CM) and Unified CM SME, tracked as CVE-2026-20230. The flaw allows unauthenticated, remote attackers to perform SSRF attacks and write files to the operating system, potentially leading to root access. Exploitation requires the WebDialer service to be enabled, which is disabled by default. Cisco has released patches for affected versions.

Full text

Cisco Unified CM Flaw Exploited After PoC Reveals File-Write Path to Root Ravie LakshmananJun 24, 2026Vulnerability / Network Security Threat actors have begun to exploit a recently disclosed critical security flaw impacting Cisco Unified Communications Manager (Unified CM) and Unified Communications Manager Session Management Edition (Unified CM SME). The vulnerability, tracked as CVE-2026-20230 (CVSS score: 8.6), is a case of improper input validation for specific HTTP requests that could allow an unauthenticated, remote attacker to conduct server-side request forgery (SSRF) attacks through an affected device. "An attacker could exploit this vulnerability by sending a crafted HTTP request to an affected device," Cisco said in an advisory released earlier this month. "A successful exploit could allow the attacker to write files to the underlying operating system that could be used later to elevate to root." In a post shared on X earlier this week, Defused Cyber said it observed active exploitation of the vulnerability in attacks. "This is currently being exploited from a single source using an unvetted PoC, with genuinely-formatted file:// file-write payloads landing on our decoys," it noted. However, for successful exploitation to occur, the WebDialer service must be enabled. It's disabled by default. To check if the WebDialer is enabled, users can complete the following steps - Log in to the Cisco Unified CM Administration interface From the Navigation menu, choose Cisco Unified Serviceability and click Go From the Tools menu, choose Control Center - Feature Services In the CTI Services section of the page, check whether the current status of the Cisco WebDialer Web Service is Started or Not Running If the status is Started, WebDialer is enabled The vulnerability has been patched in Unified CM and Unified CM SME versions 14SU6 and 15SU5. If immediate patching is not an option, it's advised to disable the WebDialer service until a fix can be applied. SSD Secure Disclosure has since published additional technical specifics of CVE-2026-20230, describing it as a flaw that allows unauthenticated attackers to arbitrarily write files in the server by leveraging the Webdialer component to obtain the true hostname of the target and ultimately achieve code execution. Cisco has yet to update the advisory to reflect the exploitation status. Last week, the network security company released security updates for a medium-severity security flaw in Catalyst SD-WAN Manager (CVE-2026-20262, CVSS score: 6.5) that has come under active exploitation in the wild. Found this article interesting? Follow us on Google News, Twitter and LinkedIn to read more exclusive content we post. SHARE     Tweet Share Share Share SHARE  cisco, Code Execution, network security, Patch Management, SSRF, Vulnerability, WebDialer ⚡ Top Stories This Week Chrome V8 Zero-Day CVE-2026-11645 Exploited in the Wild - Patch Now Researchers Build Self-Replicating AI Worm That Operates Entirely on Local, Open-Weight Models Microsoft Defender RoguePlanet Zero-Day Grants SYSTEM Access on Updated Windows Anthropic Releases Claude Fable 5, Its Most Powerful AI Yet, With Cyber Safeguards Microsoft Patches Record 206 Flaws, Including Three Zero-Days and Critical RCE Bugs Ivanti, Fortinet, and SAP Release Patches for Multiple Critical Vulnerabilities Cybersecurity Stars Awards 2026: Winners Announced Across 95 Categories ThreatsDay Bulletin: Worm Code Leaked, AI Agent Phished, Claude Code Patch + 28 New Stories New GreatXML Exploit Bypasses Windows BitLocker via Recovery Partition XML Files Agentjacking Attack Tricks AI Coding Agents Into Running Malicious Code China-Linked Hackers Backdoored Linux Login Software to Hide for Nearly a Decade Critical Splunk Enterprise Flaw Lets Attackers Run Code Without Authentication U.S. Orders Anthropic to Suspend Fable 5 and Mythos 5 Access for Foreign Nationals Over 400 Arch Linux AUR Packages Hijacked to Deploy Infostealer and eBPF Rootkit Palo Alto Warns of Active Exploitation of PAN-OS GlobalProtect VPN Flaw ⚡ Weekly Recap: Chrome 0-Day, UniFi Exploits, macOS Stealers, VPN Flaw and More ⭐ Featured Resources Get the 2026 Guide to Govern and Secure Enterprise AI Agents at Scale [Watch Demo] See Which Security Gaps Attackers Could Exploit First AI Can’t Stop Every Attack. Learn How Zero Trust Can Block What’s Unknown Have You Outgrown Your MDR? 7 Warning Signs Every CISO Should Check

Indicators of Compromise

• cve — CVE-2026-20230

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