Threats / Microsoft / CVE-2021-31979
CVE-2021-31979
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Microsoft Windows vulnerability
Microsoft Windows kernel vulnerability allowing privilege escalation. Exploited in the wild with low EPSS score.
Verdict
Today item — known-exploited.
A buffer overflow in the Windows kernel enables local attackers to escalate privileges. Active exploitation observed despite low predicted exploitation likelihood.
CISA KEV Yes · 2021-11-035EPSS 0.02634 (verify live)6CVSS 7.83CISA SSVC Exploitation: active · Automatable: no · Impact: total4
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
7 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03).
Probability (EPSS)
EPSS 0.02634 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C) · Affected: Microsoft, Windows. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-119 Memory Buffer Bounds Error — weakness family: Memory safety.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 112 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I execute a local process on the target Windows system.
Business
An attacker gains initial code execution capability on the host.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I trigger the kernel vulnerability through a crafted system call or driver interaction.
Business
The buffer overflow condition is reached, corrupting kernel memory.
3
Lateral reach — past segmentation narrative 3
Attacker
I escalate my process privileges from user mode to system/kernel level.
Business
The attacker obtains SYSTEM-level access, bypassing all user-mode security controls.
4
Data at risk — exfiltration narrative 4
Attacker
I install persistent backdoors or malware with kernel privileges.
Business
The compromised system becomes fully controlled and difficult to remediate.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05