Threats / Microsoft / CVE-2021-38646
CVE-2021-38646
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Microsoft Office vulnerability
Microsoft Office Access Connectivity Engine contains an unspecified vulnerability allowing remote code execution. This vulnerability has been exploited in the wild and linked to ransomware campaigns.
Verdict
Today item, not a backlog item.
Active exploitation in ransomware operations indicates high adversarial interest. The remote code execution capability combined with Office's ubiquitous deployment creates significant organizational risk. Immediate patching is critical.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
2 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 2022-03-28), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.04044 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Microsoft, Office. Confirm exact fixed builds in the vendor advisory.
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
Deliver malicious Office document to target user via email or web
Business
User opens document, triggering vulnerability without additional interaction
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
Exploit Access Connectivity Engine to execute arbitrary code in Office process context
Business
Attacker gains code execution with user privileges on the endpoint
3
Lateral reach — past segmentation narrative 3
Attacker
Download and execute ransomware payload or establish persistence mechanism
Business
Systems encrypted or compromised; data exfiltration and operational disruption occur
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