CVE-2026-21222: Windows 10 Information Disclosure Flaw

CVE-2026-21222 Overview

CVE-2026-21222 is an information disclosure vulnerability affecting the Windows Kernel that allows an authorized attacker to access sensitive information through improper logging practices. This vulnerability falls under CWE-532 (Insertion of Sensitive Information into Log File), where the Windows Kernel inadvertently writes sensitive data to log files that can be accessed by local users with low-level privileges.

The vulnerability requires local access to the affected system, meaning an attacker must first establish a foothold on the target machine. Once present, the attacker can leverage this flaw to extract sensitive information from kernel log files, potentially exposing credentials, security tokens, memory addresses, or other confidential data that should not be logged in plaintext.

Critical Impact

Local attackers with low-level privileges can access sensitive information logged by the Windows Kernel, potentially enabling further attacks, privilege escalation, or data exfiltration on affected Windows systems.

Affected Products

• Microsoft Windows 10 1607, 1809, 21H2, 22H2 (x86, x64, ARM64)
• Microsoft Windows 11 23H2, 24H2 (x64, ARM64)
• Microsoft Windows Server 2012 R2, 2016, 2019, 2022, 2022 23H2, 2025

Discovery Timeline

• February 10, 2026 - CVE-2026-21222 published to NVD
• February 11, 2026 - Last updated in NVD database

Technical Details for CVE-2026-21222

Vulnerability Analysis

This vulnerability stems from improper handling of sensitive data within the Windows Kernel logging mechanisms. When certain kernel operations occur, the system writes debug or operational information to log files. Due to insufficient sanitization, sensitive information that should be redacted or excluded is instead written in cleartext to these log files.

The vulnerability allows an authenticated local user to read these log files and extract sensitive information. The confidentiality impact is considered high because the exposed data could include security-critical information such as authentication tokens, memory addresses useful for bypassing ASLR, internal system state information, or other data that could facilitate subsequent attacks.

This type of vulnerability is particularly concerning in multi-user environments and enterprise deployments where multiple users share systems, as a lower-privileged user could potentially access information belonging to other users or system processes.

Root Cause

The root cause of CVE-2026-21222 is classified under CWE-532: Insertion of Sensitive Information into Log File. This weakness occurs when the Windows Kernel logging subsystem fails to properly filter or redact sensitive information before writing to log files. The kernel components responsible for generating diagnostic or operational logs do not adequately check whether the data being logged contains sensitive information that should be protected.

This design flaw results in sensitive data being persisted to disk in an accessible location, violating the principle of least privilege and creating an information disclosure pathway for local attackers.

Attack Vector

The attack requires local access to the vulnerable Windows system. An attacker with low-privilege user credentials can exploit this vulnerability without any user interaction. The attack sequence typically involves:

1. The attacker gains local access to a Windows system running an affected version
2. The attacker identifies and accesses kernel log files containing sensitive information
3. The attacker parses the log files to extract sensitive data such as credentials, tokens, or memory addresses
4. The extracted information can then be used for further attacks, including privilege escalation or lateral movement

Since the vulnerability requires local access and low privileges, it is most likely to be exploited as part of a multi-stage attack chain where an attacker has already compromised a system through other means and is seeking to escalate their access or gather intelligence for further exploitation.

Detection Methods for CVE-2026-21222

Indicators of Compromise

• Unusual access patterns to Windows kernel log files by non-administrative users
• Suspicious processes or scripts reading from %SystemRoot%\System32\LogFiles or similar kernel logging directories
• Evidence of log file copying or exfiltration to unusual locations
• Anomalous PowerShell or command-line activity involving log file enumeration

Detection Strategies

• Monitor file access events for kernel log files using Windows Security Event logs (Event ID 4663)
• Implement SentinelOne Singularity Platform with behavioral detection rules for sensitive file access patterns
• Deploy endpoint detection and response (EDR) policies to alert on bulk log file reads by non-system processes
• Use SIEM correlation rules to identify patterns of log file access followed by network exfiltration attempts

Monitoring Recommendations

• Enable enhanced auditing for file system access on directories containing kernel logs
• Configure SentinelOne agents to monitor for suspicious file access behaviors in kernel logging directories
• Establish baseline access patterns for log files and alert on deviations
• Implement real-time monitoring for processes attempting to read kernel log files

How to Mitigate CVE-2026-21222

Immediate Actions Required

• Apply the latest Microsoft security updates for all affected Windows systems immediately
• Review and restrict file system permissions on kernel log directories to limit access to administrators only
• Audit systems for evidence of exploitation, particularly unauthorized access to kernel log files
• Implement network segmentation to limit lateral movement if exploitation has occurred

Patch Information

Microsoft has released security updates to address this vulnerability. Administrators should consult the Microsoft Security Update Guide for CVE-2026-21222 for specific patch information and download links for each affected product version.

Apply patches through Windows Update, Windows Server Update Services (WSUS), or Microsoft Update Catalog based on your organization's patch management strategy. Priority should be given to systems with multiple local users or those in shared computing environments.

Workarounds

• Restrict access to kernel log directories using NTFS permissions to limit reads to the SYSTEM account and local administrators only
• Implement application control policies to prevent unauthorized processes from accessing log files
• Consider disabling non-essential kernel logging features where business requirements permit
• Deploy file integrity monitoring to detect and alert on unauthorized access to sensitive log locations

# Restrict access to kernel log directories (run as Administrator)
icacls "%SystemRoot%\System32\LogFiles" /inheritance:r
icacls "%SystemRoot%\System32\LogFiles" /grant:r "SYSTEM:(OI)(CI)F"
icacls "%SystemRoot%\System32\LogFiles" /grant:r "Administrators:(OI)(CI)F"