SharePoint 0-day uncovered (CVE-2025-53770)

[carlospolop]

🤖 Automated Content Update

This PR was automatically generated by the HackTricks News Bot based on a technical blog post.

📝 Source Information

• Blog URL: https://research.eye.security/sharepoint-under-siege/
• Blog Title: SharePoint 0-day uncovered (CVE-2025-53770)
• Suggested Section: generic-hacking/aspnet-viewstate-deserialization.md

🎯 Content Summary

ToolShell: SharePoint Server Zero-Day Exploitation Summary

Detection and Initial Vector

On the evening of July 18, 2025, Eye Security’s SOC detected a CrowdStrike Falcon EDR alert for an obfuscated .aspx web shell on an internet-facing SharePoint Server. IIS logs revealed unauthenticated POST requests to /_layouts/15/ToolPane.aspx?DisplayMode=Edit&a=/ToolPane.aspx with Referer: /_layouts/SignOut.aspx and empty 🔧 Technical Details

An unauthenticated authentication bypass in /_layouts/15/ToolPane.aspx (CVE-2025-49706) combined with a server-side control deserialization flaw (CVE-2025-49704) allows attackers to write arbitrary ASPX files into the SharePoint layouts directory by issuing a POST request with Referer: /_layouts/SignOut.aspx and empty credentials.

The deployed ASPX backdoor (spinstall0.aspx) leverages .NET reflection to load the internal System.Web.Configurat...

🤖 Agent Actions

Added new practical technique to the existing ViewState exploitation guide:

1. File modified
   • src/pentesting-web/deserialization/exploiting-__viewstate-parameter.md

2. Key additions
   • “Dumping ASP.NET Machine Keys via Reflection (SharPyShell/SharePoint ToolShell)” section explaining how to:
   – Upload/execute an ASPX page that uses reflection to call MachineKeySection.GetApplicationConfig
   – Leak ValidationKey, DecryptionKey, algorithm and compatibility mode
   – Feed those secrets into ysoserial.net to craft signed __VIEWSTATE gadgets for RCE
   • Real-world context referencing the 2025 “ToolShell” SharePoint mass-exploitation chain (CVE-2025-53770/53771).
   • Added Eye Security blog post to References.

This augments the ViewState deserializatio...

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[carlospolop]

🔗 Additional Context

Original Blog Post: https://research.eye.security/sharepoint-under-siege/

Content Categories: Based on the analysis, this content was categorized under "generic-hacking/aspnet-viewstate-deserialization.md".

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Bot Version: HackTricks News Bot v1.0