Microsoft Patch Tuesday May 2025 critical RCE fixes
Free public brief. The indicators, the detections with Splunk SPL already written (plus Elastic and KQL where they apply), and a Slack alert the next time this touches a vendor you run are in the app — free account, no card.
Microsoft patches critical RCE flaws across Windows, Office, and cloud services; no active exploitation reported.
Microsoft released critical security patches on May 13, 2025 addressing multiple remote code execution vulnerabilities across a wide range of products. The most severe flaws could allow an attacker to execute arbitrary code in the context of the logged-on user, potentially leading to privilege escalation, data theft, malware installation, or account creation depending on user privileges. Affected systems span Windows kernel and drivers, Office applications, development tools (Visual Studio, .NET), cloud services (Azure DevOps, Azure Automation), Remote Desktop services, Active Directory Certificate Services, and Hyper-V. The advisory confirms no evidence of active exploitation in the wild at the time of publication. CIS recommends immediate patching after testing, enforcement of least-privilege principles, privileged account management, security awareness training, and deployment of endpoint detection and behavior prevention capabilities.
Detection guidance
Office Application Spawning Command Interpreter or LOLBin
Office applications launching shells, script hosts or common LOLBins, which is the typical post-exploitation pattern of a client-side RCE in Office documents. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Office Application Spawning Command Interpreter or LOLBin
description: Detects Microsoft Office processes spawning shells, script hosts or common
living-off-the-land binaries. This is the typical child-process behaviour after
exploitation of a client-side code execution flaw in Office (the report describes
arbitrary code execution in the context of the logged-on user). The rule is generic
and does not depend on a specific CVE.
tags:
- attack.execution
- attack.t1203
logsource:
category: process_creation
product: windows
detection:
selection:
ParentImage|endswith:
- \WINWORD.EXE
- \EXCEL.EXE
- \POWERPNT.EXE
- \MSPUB.EXE
- \VISIO.EXE
- \OUTLOOK.EXE
Image|endswith:
- \cmd.exe
- \powershell.exe
- \pwsh.exe
- \wscript.exe
- \cscript.exe
- \mshta.exe
- \regsvr32.exe
- \rundll32.exe
- \bitsadmin.exe
- \certutil.exe
condition: selection
falsepositives:
- Legitimate Excel or Word macros and add-ins that call cmd.exe or PowerShell for
business automation
- Outlook add-ins or integrations that launch helper scripts
level: medium
id: 22b8fd71-1b47-558b-b844-4823202b5d5e
status: experimental
author: Vorant
references:
- https://www.cisecurity.org/advisory/critical-patches-issued-for-microsoft-products-may-13-2025_2025-048
Behavioural rules are generated from public reporting — validate in your environment before deploying.
Source reporting: https://www.cisecurity.org/advisory/critical-patches-issued-for-microsoft-products-may-13-2025_2025-048
What this brief leaves out
This page is the free tier: the write-up, the severity, the names. In the app the same report carries its extracted indicators, its detections (Splunk SPL already written, plus Elastic and Microsoft KQL where they apply), the actors and CVEs it names as live profiles, and the vendor research on the same campaign — the primary source the news paraphrased, cited and read directly.
It sits in a corpus of 13,854 reports from 146 sources, 616 of them written in the last seven days, and it grows through the day.
A new account starts with three days of all of it, no card, then keeps the government and CERT reporting free. Name the vendors you run and Slack hears about the reports that touch them — about forty a week that are yours, not the four hundred that are not.
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