SharePoint ToolShell Exploitation via ToolPane POST with SignOut Referer (via webserver)

ATT&CK techniques

Initial Access

Recon
Resource Dev
Initial Access
- T1190Exploit Public-Facing Application
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects POST requests to the SharePoint ToolPane.aspx endpoint carrying a spoofed SignOut.aspx referer, the unauthenticated request pattern used to exploit the ToolShell CVE-2025-53770 deserialization flaw. Adversaries leverage this request to achieve remote code execution and drop web shells, making early detection critical for catching perimeter compromise before machine-key theft.

Reporting behind it

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SharePoint ToolShell Exploitation via ToolPane POST with SignOut Referer (via webserver)

Pivot detection · T1190 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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