CVE-2021-38646
HighExploitedPublic exploitMicrosoft Office Access Connectivity Engine Remote Code Execution Vulnerability
Published Sep 15, 2021 · Updated Aug 10, 2026
Key Facts
Patch immediately- CVE-2021-38646 is a high-severity vulnerability (CVSS 7.8 v3.1) affecting 365 Apps (Microsoft), Office (Microsoft), Office 2016 (Microsoft) and 1 more product.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 28, 2022 and is known to be used in ransomware campaigns. Public exploit code is available.
- EPSS estimates a 8.0% probability of exploitation in the next 30 days.
- Fixed versions are available, including 365 Apps https://aka.ms/OfficeSecurityReleases, Office 5215.1000, Office 5381.1000.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
7.8
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
8.0%
Higher than 94.7% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings, used by ransomware
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2021-38646 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
Microsoft Office Access Connectivity Engine Remote Code Execution Vulnerability
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Mar 28, 2022 | Apr 18, 2022 | Known |
| Industry KEV feed | Mar 28, 2022 | Apr 18, 2022 | Known |
| CIRCL KEV | Mar 28, 2022 | Apr 18, 2022 | Known |
| ENISA EUVD | Mar 28, 2022 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
12 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| 365 AppsMicrosoft | See advisory | https://aka.ms/OfficeSecurityReleases |
| OfficeMicrosoft | 2013-sp1, 2016, 2019 | 5381.1000 |
| Office 2016Microsoft | See advisory | n/a |
| Office 2019Microsoft | See advisory | n/a |
Patched Releases
365 Apps
https://aka.ms/OfficeSecurityReleases
Office
5215.1000, 5381.1000, https://aka.ms/OfficeSecurityReleases
Timeline
Publicly disclosed
Sep 15, 2021
Added to CISA KEV
Mar 28, 2022
Added to Industry KEV feed
Mar 28, 2022
Added to CIRCL KEV
Mar 28, 2022
Added to ENISA EUVD
Mar 28, 2022
Last updated
Aug 10, 2026
References
- patchhttps://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-38646
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
- otherhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-38646
- otherhttps://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-38646
FAQ
Common Questions.
Microsoft Office Access Connectivity Engine Remote Code Execution Vulnerability
Affected: 365 Apps (Microsoft); Office (Microsoft) versions 2013-sp1, 2016, 2019; Office 2016 (Microsoft), among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 28, 2022 and is known to be used in ransomware campaigns.
Yes. It was added on Mar 28, 2022 with a federal remediation due date of Apr 18, 2022.
Public exploit code is available.
Fixed versions are available, including 365 Apps https://aka.ms/OfficeSecurityReleases, Office 5215.1000, Office 5381.1000.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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