Threats / Microsoft / CVE-2021-1647
CVE-2021-1647
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Microsoft Defender vulnerability
Microsoft Defender remote code execution vulnerability allowing attackers to execute arbitrary code through unspecified attack vectors.
Verdict
Today item — known-exploited.
A remote code execution flaw in Microsoft Defender enables attackers to compromise systems without authentication. Active exploitation in the wild demonstrates immediate threat; buffer overflow and improper resource validation weaknesses create execution pathways.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
4 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 0.39653 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Microsoft, Defender. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-122 Heap-based Buffer Overflow, CWE-1285 CWE-1285 — 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
Craft malicious input targeting Defender's parsing or processing logic to trigger memory corruption.
Business
Endpoint security layer fails, exposing all protected systems to direct compromise.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
Deliver payload through network communication or file interaction with Defender components.
Business
Attackers gain code execution context within security software, bypassing intended protections.
3
Lateral reach — past segmentation narrative 3
Attacker
Execute arbitrary commands with Defender's privilege level on the target system.
Business
Full system compromise possible; attacker inherits elevated access and persistence mechanisms.
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