---
title: Potential VIEWSTATE RCE Attempt on SharePoint/IIS
description: Detects potential remote code execution (RCE) attempts targeting IIS web servers running SharePoint via malicious VIEWSTATE payloads in HTTP POST requests...
url: https://www.elastic.co/docs/reference/security/prebuilt-rules/rules_building_block/initial_access_potential_rce_via_toolshell
products:
  - Elastic Security
---

# Potential VIEWSTATE RCE Attempt on SharePoint/IIS
Detects potential remote code execution (RCE) attempts targeting IIS web servers running SharePoint via malicious
VIEWSTATE payloads in HTTP POST requests. Attackers may exploit insecure deserialization in the VIEWSTATE parameter to
execute arbitrary code. This rule identifies suspicious requests containing VIEWSTATE data and other indicators of
exploitation, specifically those associated with the Toolshell exploit chain. Toolshell leverages vulnerabilities
(CVE-2025-53770 and CVE-2025-53771) for initial access, enabling adversaries to deploy a webshell, steal machine keys,
sign VIEWSTATE payloads offline, and subsequently send signed payloads to the server to achieve code execution.
**Rule type**: query
**Rule indices**:
- logs-network_traffic.http*

**Rule Severity**: medium
**Risk Score**: 47
**Runs every**: 60m
**Searches indices from**: `now-119m`
**Maximum alerts per execution**: 100
**References**:
- [[https://research.eye.security/sharepoint-under-siege/](https://research.eye.security/sharepoint-under-siege/)](https://research.eye.security/sharepoint-under-siege/)
- [[https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-53771](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-53771)](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-53771)
- [[https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-53770](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-53770)](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-53770)
- [[https://msrc.microsoft.com/blog/2025/07/customer-guidance-for-sharepoint-vulnerability-cve-2025-53770/](https://msrc.microsoft.com/blog/2025/07/customer-guidance-for-sharepoint-vulnerability-cve-2025-53770/)](https://msrc.microsoft.com/blog/2025/07/customer-guidance-for-sharepoint-vulnerability-cve-2025-53770/)

**Tags**:
- Domain: Network
- Tactic: Initial Access
- Use Case: Exploit Detection
- Data Source: Network Traffic
- Data Source: Network Traffic HTTP Logs
- Rule Type: BBR

**Version**: 1
**Rule authors**:
- Elastic

**Rule license**: Elastic License v2

### Network Traffic Setup

This rule requires network traffic logs to be collected from HTTP endpoints, focusing on IIS web servers and SharePoint sites. Ensure logging captures HTTP request and response details, including headers and request bodies for POST requests. Monitoring VIEWSTATE content is critical for detecting deserialization attacks.

## Rule Query

```kuery
data_stream.dataset : "network_traffic.http" and
    network.direction: "ingress" and
    http.request.method: "POST" and
    http.request.referrer: *SignOut.aspx and
    http.request.body.content: *__VIEWSTATE=* and
    http.request.body.bytes >= 500 and
    http.response.headers.server: Microsoft-IIS*
```

**Framework:** MITRE ATT&CK
- Tactic:
  - Name: Initial Access
- Id: TA0001
- Reference URL: [[https://attack.mitre.org/tactics/TA0001/](https://attack.mitre.org/tactics/TA0001/)](https://attack.mitre.org/tactics/TA0001/)
- Technique:
  - Name: Exploit Public-Facing Application
- Id: T1190
- Reference URL: [[https://attack.mitre.org/techniques/T1190/](https://attack.mitre.org/techniques/T1190/)](https://attack.mitre.org/techniques/T1190/)