Microsoft Windows Win32k Privilege Escalation Vulnerability
Microsoft · Windows
The Win32k component of Microsoft Windows contains a privilege escalation flaw classified as a use-after-free condition. An attacker with local access and low-privileged credentials on the system could exploit it without any user interaction to gain elevated privileges.
Win32k Elevation of Privilege Vulnerability
- Exploited
- Yes, in CISA KEV
- Reports
- 0
- Tactics
- 6/15
How an attack unfolds
Based on MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. mappings. Select a step to see the evidence.How attackers get in
What they do
What can follow
- Run Windows command-line commandsT1059.003 · Windows Command Shell
- Hide malicious codeT1027 · Obfuscated Files or Information
- System Network Configuration DiscoveryT1016 · System Network Configuration Discovery
- Collect system informationT1082 · System Information Discovery
- Talk to the attacker over web trafficT1071.001 · Web Protocols
- Symmetric CryptographyT1573.001 · Symmetric Cryptography
Exploitation timelineDated milestones for a CVE: when it was disclosed, when exploit code became public, when exploitation was confirmed, and when threat reports named it.
First seen exploited 1 day before it was disclosed. Public exploit code (Metasploit) was available 1 day before disclosure.
- Disclosedday 0
- Added to CISA KEVknown ransomware use; EU database agrees+35 days
CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.
MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. techniques
8 TechniqueOne specific attacker behaviour in MITRE ATT&CK, such as T1190 “Exploit Public-Facing Application”. IDs with a dot, like T1059.004, are sub-techniques., grouped by TacticThe attacker’s goal at a stage of an attack in MITRE ATT&CK, such as Initial Access or Persistence. Each technique belongs to one or more tactics. in kill-chain order 8Initial AccessTA0001
This vulnerability is exploited by an attacker who has obtained administrative console access on the target system. The vulnerability lies in the Win32k driver, specifically in the NtGdiResetDC function, due to improper handling of user-mode callbacks. This vulnerability has been exploited by threat actors to gain elevated privileges on Windows servers. Attackers leveraged this flaw to execute arbitrary kernel commands, allowing them to manipulate system processes and deploy additional malware to perform further malicious activities. The exploit in question is actively being used in the wild, primarily in espionage campaigns. It involves triggering a use-after-free condition by executing the ResetDC function a second time for the same handle during a callback. Once the vulnerability is exploited, attackers can manipulate memory to perform arbitrary kernel function calls with controlled parameters. This allows them to achieve their objectives, such as reading and writing kernel memory, with the same permissions as the compromised system's user.
ExecutionTA0002
Privilege EscalationTA0004
Stealth
DiscoveryTA0007
Command and ControlTA0011
This vulnerability is exploited by an attacker who has obtained administrative console access on the target system. The vulnerability lies in the Win32k driver, specifically in the NtGdiResetDC function, due to improper handling of user-mode callbacks. This vulnerability has been exploited by threat actors to gain elevated privileges on Windows servers. Attackers leveraged this flaw to execute arbitrary kernel commands, allowing them to manipulate system processes and potentially deploy additional malware or perform further malicious activities. The exploit in question is actively being used in the wild, primarily in espionage campaigns. It involves triggering a use-after-free condition by executing the ResetDC function a second time for the same handle during a callback. Once the vulnerability is exploited, attackers can manipulate memory to perform arbitrary kernel function calls with controlled parameters. This allows them to achieve their objectives, such as reading and writing kernel memory, with the same permissions as the compromised system's user.
Detection
0 rules for this CVE · 273 general rules for its techniquesRules for this CVE
0Sigma ruleAn open, vendor-neutral detection rule for log data. Security teams convert Sigma rules into searches for their own SIEM. that reference CVE-2021-40449 directly.CVE-specific rules are not available in this build. Search SigmaHQ ↗
General rules for this CVE’s techniques
These detect the technique in general, not this specific vulnerability.
PhishingT156614 general rules
- CVE-2021-31979 CVE-2021-33771 Exploitscriticaltest
- CVE-2021-31979 CVE-2021-33771 Exploits by Sourgumcriticaltest
- HTML Help HH.EXE Suspicious Child Processhightest
- Okta FastPass Phishing Detectionhightest
- Phishing Pattern ISO in Archivehightest
- Potential Malicious Usage of CloudTrail System Managerhightest
- Suspicious External WebDAV Executionhightest
- Suspicious HH.EXE Executionhightest
Exploitation for Privilege EscalationT106831 general rules
- Exploiting CVE-2019-1388criticalstable
- Audit CVE Eventcriticaltest
- HackTool - SysmonEOP Executioncriticaltest
- InstallerFileTakeOver LPE CVE-2021-41379 File Create Eventcriticaltest
- Possible Coin Miner CPU Priority Paramcriticaltest
- Potential CVE-2021-41379 Exploitation Attemptcriticaltest
- Potential SystemNightmare Exploitation Attemptcriticaltest
- Sudo Privilege Escalation CVE-2019-14287 - Builtincriticaltest
Windows Command ShellT1059.00346 general rules
- Elise Backdoor Activitycriticaltest
- Rorschach Ransomware Execution Activitycriticaltest
- ZxShell Malwarecriticaltest
- HackTool - CrackMapExec Execution Patternshighstable
- AWS EC2 Startup Shell Script Changehightest
- Conhost.exe CommandLine Path Traversalhightest
- Exploited CVE-2020-10189 Zoho ManageEnginehightest
- Exploiting SetupComplete.cmd CVE-2019-1378hightest
Obfuscated Files or InformationT102795 general rules
- Turla Group Commands May 2020criticaltest
- Potential Emotet Activityhighstable
- Base64 Encoded PowerShell Command Detectedhightest
- File Decoded From Base64/Hex Via Certutil.EXEhightest
- File In Suspicious Location Encoded To Base64 Via Certutil.EXEhightest
- Invoke-Obfuscation CLIP+ Launcherhightest
- Invoke-Obfuscation CLIP+ Launcher - PowerShellhightest
- Invoke-Obfuscation CLIP+ Launcher - PowerShell Modulehightest
System Network Configuration DiscoveryT101612 general rules
- OpenCanary - SNMP OID Requesthightest
- Potential Pikabot Discovery Activityhightest
- Potential Recon Activity Via Nltest.EXEmediumtest
- Suspicious Network Connection to IP Lookup Service APIsmediumtest
- Cisco Discoverylowtest
- Firewall Configuration Discovery Via Netsh.EXElowtest
- Local Firewall Rules Enumeration Via NetFirewallRule Cmdletlowtest
- Nltest.EXE Executionlowtest
System Information DiscoveryT108233 general rules
- HackTool - PCHunter Executionhightest
- HackTool - winPEAS Executionhightest
- HackTool - WinPwn Executionhightest
- HackTool - WinPwn Execution - ScriptBlockhightest
- Network Reconnaissance Activityhightest
- Potential GobRAT File Discovery Via Grephightest
- Suspicious Kernel Dump Using Dtracehightest
- Bitbucket User Details Export Attempt Detectedmediumtest
Web ProtocolsT1071.00142 general rules
- Ursnif Malware C2 URL Patterncriticalstable
- HackTool - BabyShark Agent Default URL Patterncriticaltest
- PwnDrp Accesscriticaltest
- Ursnif Malware Download URL Patternhighstable
- APT User Agenthightest
- APT40 Dropbox Tool User Agenthightest
- Bitsadmin to Uncommon IP Server Addresshightest
- Bitsadmin to Uncommon TLDhightest
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
What security researchers reported
Not named in any threat report yetAlso mentioned in 50 community threat pulses (AlienVault OTX)
Weaker evidencePulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.
- Actively_Exploited_Kev | Oct 29, 202628 Oct 2026
- Actively_Exploited_Kev | Oct 28, 202627 Oct 2026
- Actively_Exploited_Kev | Oct 27, 202626 Oct 2026
- Actively_Exploited_Kev | Oct 24, 202623 Oct 2026
- Actively_Exploited_Kev | Oct 23, 202622 Oct 2026
- Actively_Exploited_Kev | Oct 22, 202621 Oct 2026
- 44 more on OTX