CVE-2021-31979 KEV High · 7.8 EPSS 4.5%
Microsoft Windows Kernel Privilege Escalation Vulnerability
Microsoft · Windows
Summary
A memory-safety flaw in the Windows kernel (Microsoft Windows), classified as an improper restriction of operations within the bounds of a memory buffer, allows elevation of privilege. An attacker needs local access and low-privilege authenticated credentials on the system, requires no user interaction, and can gain higher privileges that affect confidentiality, integrity, and availability.
Official description · NVD
Windows Kernel Elevation of Privilege Vulnerability
Priority scorePatchfirst’s 0 to 100 ranking. It adds points for CISA KEV listing, ransomware use, EPSS, threat reports, public exploit code and CVSS. Every CVE page shows the breakdown. Breakdown
61.8 / 100
- Exploited
- Yes, in CISA KEV
- Reports
- 0
- Tactics
- 1/15
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.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.
- First seen exploitedVulnCheck KEV evidence1 day before
- Disclosedday 0
- Added to CISA KEVEU database agrees+4 mo
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
2 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, 2 cited passages 2Privilege EscalationTA0004
Exploitation for Privilege Escalation T1068 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details.
AI mapping from the description · how it is exploited
Kernel EoP vulnerability enables privilege escalation exploitation
Windows Kernel Elevation of Privilege Vulnerability
Abuse Elevation Control Mechanism T1548 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details.
AI mapping from the description · primary impact
Elevation of privilege yields higher-privileged access
Windows Kernel Elevation of Privilege Vulnerability
Detection
2 rules for this CVE · 55 general rules for its techniquesRules for this CVE
2Sigma ruleAn open, vendor-neutral detection rule for log data. Security teams convert Sigma rules into searches for their own SIEM. that reference CVE-2021-31979 directly.- CVE-2021-31979 CVE-2021-33771 Exploitscriticaltest
- CVE-2021-31979 CVE-2021-33771 Exploits by Sourgumcriticaltest
General rules for this CVE’s techniques
These detect the technique in general, not this specific vulnerability.
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
Abuse Elevation Control MechanismT154824 general rules
- Abused Debug Privilege by Arbitrary Parent Processeshightest
- COM Hijack via Sdclthightest
- Credential Dumping Attempt Via Svchosthightest
- Potential Privilege Escalation via Local Kerberos Relay over LDAPhightest
- Regedit as Trusted Installerhightest
- Vulnerable Netlogon Secure Channel Connection Allowedhightest
- Registry Hive File Staged Outside Standard User Profile Pathhighexperimental
- Linux Doas Conf File Creationmediumstable
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