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

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  cisco, Code Execution, network security, Patch Management, SSRF, Vulnerability, WebDialer ⚡ Top Stories This Week U.S. Orders Anthropic to Suspend Fable 5 and Mythos 5 Access for Foreign Nationals Microsoft Patches Record 206 Flaws, Including Three Zero-Days and Critical RCE Bugs Chrome V8 Zero-Day CVE-2026-11645 Exploited in the Wild - Patch Now Over 400 Arch Linux AUR Packages Hijacked to Deploy Infostealer and eBPF Rootkit Critical Splunk Enterprise Flaw Lets Attackers Run Code Without Authentication Cybersecurity Stars Awards 2026: Winners Announced Across 95 Categories Anthropic Releases Claude Fable 5, Its Most Powerful AI Yet, With Cyber Safeguards Ivanti, Fortinet, and SAP Release Patches for Multiple Critical Vulnerabilities Agentjacking Attack Tricks AI Coding Agents Into Running Malicious Code New GreatXML Exploit Bypasses Windows BitLocker via Recovery Partition XML Files ⚡ Weekly Recap: Chrome 0-Day, UniFi Exploits, macOS Stealers, VPN Flaw and More Palo Alto Warns of Active Exploitation of PAN-OS GlobalProtect VPN Flaw 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 ThreatsDay Bulletin: Worm Code Leaked, AI Agent Phished, Claude Code Patch + 28 New Stories China-Linked Hackers Backdoored Linux Login Software to Hide for Nearly a Decade ⭐ Featured Resources Get the 2026 Guide to Govern and Secure Enterprise AI Agents at Scale Have You Outgrown Your MDR? 7 Warning Signs Every CISO Should Check AI Can’t Stop Every Attack. Learn How Zero Trust Can Block What’s Unknown [Watch Demo] See Which Security Gaps Attackers Could Exploit First