Describe the behaviour you want to detect. SARA writes a starting Sigma rule with MITRE tags, false-positive guidance, and detection-engineering context. Anonymous, no account, best-effort generic detection.
title: Potential CVE-2023-33107 SharePoint Server Information Disclosure Exploitation
id: faceb173-fe7d-4535-b488-ab76cd6ba336
status: experimental
description: |
Detects potential exploitation of CVE-2023-33107, a .NET deserialization vulnerability in Microsoft SharePoint Server.
This vulnerability allows unauthenticated attackers to disclose information by sending crafted HTTP requests to SharePoint endpoints.
This rule looks for characteristic URI patterns and query parameters associated with known Proof-of-Concept (PoC) exploits.
CVSS: 8.6 (High) | KEV Status: Listed by CISA.
references:
- https://nvd.nist.gov/vuln/detail/CVE-2023-33107
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-33107
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog
author: SARA Detection Engineering
date: 2026-08-18
tags:
- attack.t1190
- attack.initial_access
logsource:
category: webserver
product:
detection:
selection_target:
cs-uri-stem|contains:
- '/_layouts/'
- '/_vti_bin/'
- '/_api/'
selection_payload:
cs-uri-query|contains:
- '__VIEWSTATE'
- 'TypeDescriptor'
- 'System.Workflow.ComponentModel'
- 'BinaryFormatter'
- 'ObjectStateFormatter'
- 'ActivitySurrogateSelector'
filter_legit:
cs-user-agent|contains:
- 'SharePoint'
- 'Microsoft Office'
- 'MSWAC'
condition: selection_target and selection_payload and not filter_legit
fields:
- c-ip
- cs-method
- cs-uri-stem
- cs-uri-query
- cs-user-agent
- sc-status
falsepositives:
- Legitimate SharePoint administrative workflows or custom workflows utilizing complex serialized payloads.
- Vulnerability scanners (e.g., Nessus, Qualys) configured to audit SharePoint infrastructure.
level: high
Sigma is the open, vendor-neutral format for log-based detections. One rule, written once, converts to Splunk SPL, Elastic ES|QL, KQL for Microsoft Sentinel, Sumo, Chronicle, QRadar, and more. Detection engineers love it for the same reason ATT&CK is the lingua franca for tactics — Sigma is the lingua franca for the queries that detect them.
You've got a fresh write-up of a TTP and need a starting detection in your stack today. Generate, tune, ship.
Pair-program with SARA: the generator produces the skeleton, the engineer learns by tuning, the team commits the result.
You have a rule in one query language; describe it in English and get the Sigma version + conversions to every other backend.
Sketch a detection idea in 30 seconds before investing in a full DE sprint.
SARA Open ships an OpenAI-compatible API. Call POST /api/v1/sigma — Plain English in, valid Sigma YAML out, with MITRE tags and false-positive guidance.
curl -X POST https://sara-open.sirp.io/api/v1/sigma \
-H "Authorization: Bearer $SARA_API_KEY" \
-H "Content-Type: application/json" \
-d '{"description": "PowerShell encoded command from Office"}'
Read the API reference →