CVE-2019-20627 in AutoUpdater.NET
Summary
by MITRE
AutoUpdater.cs in AutoUpdater.NET before 1.5.8 allows XXE.
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Analysis
by VulDB Data Team • 04/18/2024
The vulnerability identified as CVE-2019-20627 represents a critical XML External Entity processing flaw within the AutoUpdater.NET library version 1.5.7 and earlier. This issue exists in the AutoUpdater.cs component which is commonly used by .NET applications to facilitate automatic software updates. The vulnerability arises from insufficient input validation when processing XML responses from update servers, creating a pathway for malicious actors to exploit the application's XML parser through external entity references.
This vulnerability falls under the CWE-611 weakness category, which specifically addresses Improper Restriction of XML External Entity Reference. The flaw enables attackers to perform various malicious activities including but not limited to server-side request forgery attacks, internal network reconnaissance, and potential data exfiltration from vulnerable systems. When an application using the affected AutoUpdater.NET library processes an update response containing malicious XML with external entity declarations, the XML parser will attempt to resolve these entities, potentially leading to unauthorized access to internal resources or execution of arbitrary code.
The operational impact of this vulnerability is significant for organizations relying on AutoUpdater.NET for their software update mechanisms. Attackers can craft specially formatted update feeds that, when processed by vulnerable applications, can cause the application to make unintended network requests to internal systems or external attacker-controlled servers. This behavior can be leveraged to bypass firewalls, perform internal port scans, or even exfiltrate sensitive data from within the organization's network perimeter. The vulnerability is particularly dangerous because it can be exploited without requiring user interaction, making it a stealthy attack vector that can go unnoticed for extended periods.
Mitigation strategies for this vulnerability should prioritize immediate upgrade to AutoUpdater.NET version 1.5.8 or later, which contains the necessary fixes to prevent XML external entity processing. Organizations should also implement network monitoring to detect unusual outbound connections that may indicate exploitation attempts. Additional protective measures include configuring XML parsers to disable external entity resolution entirely, implementing proper input validation for all XML content, and conducting regular security assessments of update mechanisms within applications. From an ATT&CK framework perspective, this vulnerability maps to technique T1071.004 (Application Layer Protocol: DNS) and T1133 (External Remote Services) as attackers can leverage the update mechanism to establish covert communication channels and access internal network resources through the compromised update process.