CVE-2018-17256 in Umbraco
Summary
by MITRE
Persistent cross-site scripting (XSS) vulnerability in Umbraco CMS 7.12.3 allows authenticated users to inject arbitrary web script via the Header Name of a content (Blog, Content Page, etc.). The vulnerability is exploited when updating or removing public access of a content.
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Analysis
by VulDB Data Team • 04/15/2020
The CVE-2018-17256 vulnerability represents a critical persistent cross-site scripting flaw within Umbraco CMS version 7.12.3 that demonstrates how authenticated users can manipulate content management interfaces to execute malicious scripts. This vulnerability specifically targets the Header Name field within content elements such as blogs and content pages, creating a persistent threat vector that can affect all users who access the compromised content. The flaw arises from inadequate input validation and output encoding mechanisms within the CMS's content management subsystem, where user-supplied data is not properly sanitized before being stored and subsequently rendered in web pages. The vulnerability's persistence stems from the fact that malicious scripts injected into the Header Name field are stored in the database and executed every time the content is accessed, making it particularly dangerous for content administrators who may inadvertently expose themselves and their users to malicious code execution.
The technical exploitation of this vulnerability requires an authenticated user with sufficient privileges to modify content elements within the Umbraco CMS interface, typically encompassing roles such as editors or administrators who can manage content pages and blog posts. When an attacker modifies the Header Name field with malicious script content, the vulnerability is triggered during the content update or public access removal process, as the system fails to properly sanitize the input before storing it. The attack vector specifically targets the content management workflow where users interact with the CMS interface to modify existing content, making it particularly insidious as it can be concealed within legitimate content management activities. The vulnerability operates at the application layer and falls under CWE-79 - Improper Neutralization of Input During Web Page Generation, which is a fundamental weakness in web application security that enables attackers to inject malicious scripts into web pages viewed by other users. This weakness is further classified under the OWASP Top 10 2017 category A03: Injection, specifically targeting cross-site scripting vulnerabilities.
The operational impact of CVE-2018-17256 extends beyond simple script execution, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, data exfiltration, and redirection to malicious websites. The persistent nature of the vulnerability means that once a malicious script is injected, it continues to execute for every user who accesses the compromised content, potentially affecting thousands of users over time. Attackers can leverage this vulnerability to steal session cookies, which would allow them to impersonate legitimate users and gain unauthorized access to the CMS administration interface. The vulnerability also enables attackers to redirect users to phishing sites or malicious domains, potentially leading to further compromise of the organization's infrastructure. Additionally, the attack can be used to deface websites, inject advertisements, or perform other malicious activities that could damage the organization's reputation and potentially lead to regulatory compliance issues.
Organizations should implement multiple layers of defense to mitigate the risks associated with CVE-2018-17256, starting with immediate patching of affected Umbraco CMS installations to version 7.13.0 or later, which contains the necessary security fixes. Input validation and output encoding should be strengthened throughout the application, particularly in fields that accept user-generated content, implementing proper HTML escaping and content sanitization techniques. The principle of least privilege should be enforced to limit the ability of authenticated users to modify critical content fields, while also implementing regular security audits and monitoring for suspicious content modifications. Security awareness training for content administrators is crucial to prevent accidental exploitation through social engineering or insider threats. Additionally, organizations should consider implementing web application firewalls and content security policies to detect and block malicious script injection attempts, while maintaining comprehensive logging and monitoring of content management activities to quickly identify and respond to potential exploitation attempts. The vulnerability also highlights the importance of following secure coding practices and conducting regular security assessments to identify similar weaknesses in application code, aligning with ATT&CK technique T1059.001 - Command and Scripting Interpreter: PowerShell and T1566.001 - Phishing: Spearphishing Attachment, which emphasize the need for robust input validation and user behavior monitoring in web applications.