CVE-2026-85880

Microsoft Windows

score 85Known exploited · added 2026-09-08watchlist: microsoft

Summary

Microsoft Windows Heap-Based Buffer Overflow Vulnerability

Microsoft Windows Advanced Local Procedure Call contains a heap-based buffer overflow vulnerability that allows an attacker to elevate privileges locally.

Published 2026-09-08 · first seen here 2026-10-10

CISA required action (due 2026-09-22): Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Analysis & write-ups

Mind the (Patch) Gap, Part 2: Fake Websites Used to Deploy Chrome & Windows 0-Day Exploits · Volexity

Where it shows in your logs

Windows or Active Directory · Memory corruption (overflow, use-after-free) high confidence

What to look for

Crashes or restarts of the vulnerable process (Windows Error Reporting, core dumps), especially repeated ones
The vulnerable process spawning children it never normally starts
Processes running as SYSTEM whose parent is a normal user process
New local or domain admin accounts, or users added to privileged groups
Unusual logons (type 3 or 10) to servers right before suspicious processes start

Data sources

Process creation · ATT&CK DS0009 Process Creation

Sentinel: DeviceProcessEventsSecurityEvent (4688)Sysmon Event ID 1_Im_ProcessCreate
Splunk: Endpoint.ProcessesXmlWinEventLog:Microsoft-Windows-Sysmon/OperationalWinEventLog:Security (4688)
CrowdStrike: ProcessRollup2SyntheticProcessRollup2

Authentication and sessions · ATT&CK DS0028 Logon Session Creation / DS0002 User Account Authentication

Sentinel: SigninLogsSecurityEvent (4624, 4625, 4648)DeviceLogonEventsIdentityLogonEvents_Im_Authentication
Splunk: Authentication.Authenticationpan:globalprotectVPN sourcetypes
CrowdStrike: UserLogonUserLogonFailed2Falcon Identity Protection events

Account and group changes · ATT&CK DS0002 User Account Creation / Modification

Sentinel: SecurityEvent (4720, 4728, 4732, 4756)AuditLogsIdentityDirectoryEvents
Splunk: Change.All_Changes (Account_Management)WinEventLog:Security (4720, 4732)
CrowdStrike: UserAccountCreatedUserAccountAddedToGroup

A generic baseline worked out from the product type and weakness (CWE-122, CWE-908), not a detection. Check table and field names against your environment. Hunt queries for Sigma, Splunk, Sentinel and CrowdStrike are coming.

News & advisories

CVE-2026-85880 Windows Advanced Local Procedure Call (ALPC) Elevation of Privilege Vulnerability · Microsoft MSRC
14th September – Threat Intelligence Report · Check Point Research