Detect Microsoft Windows Type Confusion Vulnerability (CVE-2026-21519) in Google Chronicle
Detects exploitation of CVE-2026-21519, a type confusion vulnerability (CWE-843) in Microsoft Windows. Type confusion vulnerabilities occur when code allocates or initializes a resource using one type but accesses it using an incompatible type, leading to out-of-bounds memory access, arbitrary code execution, or privilege escalation. This CVE is listed on the CISA Known Exploited Vulnerabilities catalog, indicating active exploitation in the wild.
MITRE ATT&CK
YARA-L Detection Query
rule cve_2026_21519_windows_type_confusion {
meta:
author = "df00tech Detection Engineering"
description = "Detects potential exploitation of CVE-2026-21519 Windows type confusion vulnerability"
severity = "CRITICAL"
priority = "HIGH"
reference = "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21519"
events:
(
$e.metadata.event_type = "PROCESS_LAUNCH"
and (
(
$e.principal.process.file.full_path = /(?i)(lsass\.exe|winlogon\.exe|csrss\.exe)$/
and not $e.target.process.file.full_path = /(?i)(conhost\.exe|werfault\.exe|WerFaultSecure\.exe)$/
)
or (
$e.target.process.command_line = /(?i)(SeDebugPrivilege|SeImpersonatePrivilege|SeAssignPrimaryTokenPrivilege)/
)
)
)
or (
$e.metadata.event_type = "DRIVER_LOAD"
and not $e.principal.process.file.full_path = /(?i)(MsMpEng\.exe|services\.exe|wininit\.exe|TrustedInstaller\.exe)$/
)
or (
$e.metadata.event_type = "SERVICE_CREATION"
and $e.target.resource.attribute.labels["service_file_path"] = /(?i)(\\AppData\\|\\Temp\\|\.tmp)/
)
condition:
$e
}Google Chronicle YARA-L rule detecting Windows type confusion exploitation through process anomalies, privilege token manipulation, driver loads from untrusted initiators, and service creation from temporary or user-writable paths.
Data Sources
Required Tables
False Positives & Tuning
- Security software performing authorized kernel operations triggering driver load UDM events
- Enterprise application packaging tools creating services with staging paths in user directories
- IT helpdesk tools that legitimately spawn processes under winlogon for session management
- Developer environment toolchains that request debug privileges for authorized profiling
Other platforms for CVE-2026-21519
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Simulate Anomalous Child Process from Winlogon
Expected signal: Sysmon EventID 1 showing cmd.exe or similar process with an unexpected parent, Windows Security EventID 4688 capturing the new process creation with command line arguments.
- Test 2Privilege Token Enumeration via Command Line
Expected signal: Windows Security EventID 4688 with CommandLine containing privilege-related arguments, Sysmon EventID 1 capturing the full process creation with integrity level.
- Test 3Suspicious Service Installation from Temp Directory
Expected signal: Windows System EventID 7045 (new service installed) with ServiceImagePath pointing to %TEMP%, Sysmon EventID 13 capturing registry writes for the new service key under HKLM\SYSTEM\CurrentControlSet\Services.
- Test 4Unsigned Driver Load Simulation via Sysmon
Expected signal: Sysmon EventID 6 (DriverLoad) with the ImageLoaded path pointing to a non-standard location and the initiating process being a user-mode application rather than services.exe or wininit.exe.
Unlock Pro Content
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