Threats / Microsoft / CVE-2021-40450
CVE-2021-40450
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
Microsoft Win32k vulnerability
Microsoft Win32k privilege escalation vulnerability exploited in the wild. Allows attackers to elevate privileges on affected systems.
Verdict
Today item — known-exploited.
A privilege escalation flaw in Win32k has been actively exploited. Low EPSS score suggests limited automated exploitation potential, but confirmed wild exploitation indicates targeted attacks. Patching is recommended for exposed systems.
CISA KEV Yes · 2022-04-255EPSS 0.02076 (verify live)6CVSS 7.83CISA SSVC Exploitation: active · Automatable: no · Impact: total4
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
1 independent public report 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 2022-04-25).
Probability (EPSS)
EPSS 0.02076 — 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:U/RL:O/RC:C) · Affected: Microsoft, Win32k. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
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 194 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 code with limited privileges on a target system running vulnerable Win32k.
Business
An attacker gains foothold on employee workstations or servers, bypassing initial access controls.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I exploit the Win32k vulnerability to escalate my privileges to system or administrator level.
Business
Elevated privileges enable lateral movement, persistence mechanisms, and access to sensitive data or critical system functions.
3
Lateral reach — past segmentation narrative 3
Attacker
I use elevated access to install backdoors, steal credentials, or modify system configurations.
Business
Compromise deepens across infrastructure; attackers establish persistent presence and exfiltrate confidential information.
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
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by microsoftCNA
Credited with finding itH4iiluv of 73lab with Qingtengfinder
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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