An arbitrary file upload vulnerability in Umbraco CMS v16.3.3 allows attackers to execute arbitrary code via uploading a crafted PDF file.
Description
An arbitrary file upload vulnerability in Umbraco CMS v16.3.3 allows attackers to execute arbitrary code via uploading a crafted PDF file.
AI Analyst Comment
Remediation
Update An arbitrary file upload vulnerability in Umbraco CMS Multiple Products to the latest version. Monitor for exploitation attempts and review access logs.
Executive Summary:
A critical vulnerability has been identified in Umbraco CMS, designated CVE-2025-67288. This flaw allows an unauthenticated attacker to upload a malicious file, leading to arbitrary code execution and a complete compromise of the affected server. Due to its maximum CVSS score of 10.0, this vulnerability poses a severe and immediate threat to the confidentiality, integrity, and availability of the system.
Vulnerability Details
CVE-ID: CVE-2025-67288
Affected Software: Umbraco CMS
Affected Versions: Version 16.3.3 is confirmed vulnerable. See vendor advisory for a complete list of affected versions.
Vulnerability: The vulnerability is an arbitrary file upload flaw within the Umbraco CMS. The application fails to properly validate files uploaded to the server, specifically crafted PDF files. An unauthenticated attacker can create a malicious file (e.g., a web shell) and disguise it as a PDF, bypassing the system's file type checks. Once the file is uploaded to a web-accessible directory on the server, the attacker can then access it via a URL to execute the embedded code with the permissions of the web server process.
Business Impact
This vulnerability is rated as critical severity with a CVSS score of 10.0, representing the highest possible risk. Successful exploitation grants an attacker complete control over the web server, enabling them to execute arbitrary code. Potential consequences include theft of sensitive data (customer information, credentials, intellectual property), website defacement, deployment of ransomware, or using the compromised server as a pivot point to attack other internal network resources. This poses a direct and severe risk to business operations, brand reputation, and data security.
Remediation Plan
Immediate Action: Immediately update all instances of Umbraco CMS to the latest patched version as recommended by the vendor. After applying the update, it is crucial to monitor for any signs of post-remediation exploitation attempts and thoroughly review historical access logs for indicators of compromise that may have occurred prior to patching.
Proactive Monitoring: Monitor web server logs (e.g., IIS logs) for unusual POST requests to file upload endpoints and for direct requests to non-standard files (e.g.,
.aspx,.ashx) in media or upload directories. Implement File Integrity Monitoring (FIM) to alert on the creation of new, unauthorized executable files in web directories. Monitor for anomalous processes spawned by the web server's worker process (e.g.,w3wp.exe).Compensating Controls: If patching is not immediately possible, implement the following controls:
Exploitation Status
Public Exploit Available: False
Analyst Notes: As of December 22, 2025, there are no known public exploits or active exploitation campaigns targeting this vulnerability. However, due to the critical CVSS score of 10.0 and the simplicity of the attack vector, threat actors are highly likely to develop and deploy exploits rapidly. Organizations should operate under the assumption of imminent exploitation.
Analyst Recommendation
Given the critical severity (CVSS 10.0) of this vulnerability, which allows for unauthenticated remote code execution, immediate action is required. Although CVE-2025-67288 is not currently listed on the CISA KEV catalog, its high impact and low attack complexity make it a prime target for opportunistic and sophisticated threat actors. We strongly recommend patching all vulnerable Umbraco CMS instances on an emergency basis, without delay. If patching is not feasible, the compensating controls listed above must be implemented immediately while actively hunting for any indicators of compromise.