CVE-2021-38646 Microsoft Office Access Connectivity Engine Remote Code Execution Vulnerability
Microsoft Office Access Connectivity Engine contains an unspecified vulnerability which can allow for remote code execution.
From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.
Should You Worry?
- CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 28 Mar 2022.
- CISA lists it as known to be used in ransomware campaigns.
- Rated High severity (CVSS 7.8, scored by Vendor).
- It has been in the catalogue for 1,684 days. Systems still unpatched now have almost certainly been scanned for it.
What It Is
Microsoft Office Access Connectivity Engine Remote Code Execution Vulnerability
Affected Versions
| Product | Versions |
|---|---|
| Microsoft Microsoft 365 Apps for Enterprise | 16.0.1 to before https://aka.ms/OfficeSecurityReleases |
| Microsoft Microsoft Office 2013 Service Pack 1 | 15.0.0 to before 5381.1000 |
| Microsoft Microsoft Office 2016 | 16.0.0 to before 5215.1000 |
| Microsoft Microsoft Office 2019 | 19.0.0 to before https://aka.ms/OfficeSecurityReleases |
From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.
What To Do Now
- 1
Find it
Search your asset inventory and external attack surface for Microsoft Office. Include cloud images, appliances and anything a supplier runs for you.
Attack Surface Management - 2
- 3
Hunt for compromise
If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.
Incident Response - 4
Prove it is fixed
Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.
Penetration Testing
Vendor Advisories
The Compliance Clock
General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.
Not Sure If You Are Exposed?
Our attack surface and vulnerability teams can check your internet-facing estate for CVE-2021-38646 and every other exploited flaw on the list.