CVE-2019-20627
📋 TL;DR
CVE-2019-20627 is an XML External Entity (XXE) vulnerability in AutoUpdater.NET's AutoUpdater.cs component that allows attackers to read arbitrary files, conduct server-side request forgery (SSRF), or potentially execute code by processing malicious XML update manifests. This affects any application using vulnerable versions of AutoUpdater.NET for automatic updates. The vulnerability is particularly dangerous because it can be exploited through the update mechanism that applications typically trust.
💻 Affected Systems
- AutoUpdater.NET
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution on the affected system, complete system compromise, data exfiltration, and lateral movement within the network.
Likely Case
Arbitrary file read leading to sensitive information disclosure (credentials, configuration files) and potential SSRF attacks against internal services.
If Mitigated
Limited impact with proper network segmentation, file system permissions, and XML parser hardening.
🎯 Exploit Status
Exploitation requires the attacker to control or manipulate the XML update manifest, which could be achieved through man-in-the-middle attacks, DNS poisoning, or compromising update servers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.5.8 and later
Vendor Advisory: https://github.com/ravibpatel/AutoUpdater.NET/releases/tag/v1.5.8
Restart Required: Yes
Instructions:
1. Update AutoUpdater.NET package to version 1.5.8 or later via NuGet. 2. Rebuild and redeploy affected applications. 3. Test update functionality to ensure compatibility.
🔧 Temporary Workarounds
Disable XML external entity processing
allConfigure XML parser to disable DTD processing and external entity resolution
XmlReaderSettings settings = new XmlReaderSettings();
settings.DtdProcessing = DtdProcessing.Prohibit;
settings.XmlResolver = null;
Disable automatic updates
allTemporarily disable AutoUpdater.NET functionality until patched
AutoUpdater.StartMode = StartMode.Manual;
// Or remove AutoUpdater.Start() calls
🧯 If You Can't Patch
- Implement network controls to restrict update traffic to trusted sources only
- Use application allowlisting to prevent execution of unauthorized processes
🔍 How to Verify
Check if Vulnerable:
Check the AutoUpdater.NET package version in your project's packages.config or .csproj file for versions < 1.5.8Check Version:
Get-Package -ProjectName [YourProjectName] | Where-Object {$_.Id -eq 'AutoUpdater.NET'} | Select-Object VersionVerify Fix Applied:
Verify the installed AutoUpdater.NET package version is 1.5.8 or higher and test update functionality with a known-good manifest📡 Detection & Monitoring
Log Indicators:
- Unusual XML parsing errors
- Unexpected file access attempts from update process
- Network connections to unexpected domains during updates
Network Indicators:
- HTTP requests to unusual domains during update checks
- Large or unusual XML payloads in update traffic
SIEM Query:
source="application_logs" AND ("AutoUpdater" OR "update.xml") AND (error OR exception OR "file not found")🔗 References
- https://github.com/ravibpatel/AutoUpdater.NET/commit/1dc25f2bea6ea522dbac1512b5563c4746d539c3
- https://github.com/ravibpatel/AutoUpdater.NET/releases/tag/v1.5.8
- https://www.doyler.net/security-not-included/autoupdater-net-vulnerability
- https://github.com/ravibpatel/AutoUpdater.NET/commit/1dc25f2bea6ea522dbac1512b5563c4746d539c3
- https://github.com/ravibpatel/AutoUpdater.NET/releases/tag/v1.5.8
- https://www.doyler.net/security-not-included/autoupdater-net-vulnerability
