Threats / Microsoft / CVE-2021-40449
CVE-2021-40449
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Microsoft Windows vulnerability
Windows privilege escalation vulnerability exploited in active ransomware campaigns. Authenticated users can escalate privileges via use-after-free flaw.
Verdict
Today item, not a backlog item.
High-severity privilege escalation affecting Windows systems. Active exploitation in ransomware operations with 91.5% predicted exploitation likelihood. Requires prior authentication but enables full system compromise.
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Public proof-of-concept exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
14 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 2021-11-17), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.74129 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Microsoft, Windows. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-416 Use After Free — weakness family: Memory safety.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
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
Gain initial access to Windows system with standard user credentials through phishing, credential compromise, or lateral movement.
Business
Attacker establishes foothold within network perimeter with limited privileges.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
Trigger use-after-free condition in Windows kernel to escalate from authenticated user to SYSTEM privileges.
Business
Attacker obtains unrestricted control over compromised host.
3
Lateral reach — past segmentation narrative 3
Attacker
Deploy ransomware payload with system-level permissions across enterprise infrastructure.
Business
Critical business systems encrypted, operations halted, ransom demanded.
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