Microsoft Office Remote Code Execution Vulnerability

cisa required action Apply updates per vendor instructions.

1. 2021-03-11 Published
2. 2021-11-03 Added to CISA KEV
3. 2021-11-17 CISA patch deadline
4. 2025-02-04 CISA SSVC: exploitation active

Added

5 y ago (2021-11-03)

Patch by

2021-11-17 (4 y ago)

Ransomware

Not known

Required action

Apply updates per vendor instructions.

Vendor, product

Microsoft, Office

CISA name

Microsoft Office Remote Code Execution Vulnerability

How it is exploited and what it leads to, in MITRE ATT&CK terms.

• T1203 Exploitation for Client Execution exploitation

kev release 2025-07-28, att&ck v16.1. KEV to ATT&CK mappings by the MITRE Center for Threat-Informed Defense (Mappings Explorer, Apache-2.0). © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. Terms of use

Exploitation

Active, exploited in the wild

Automatable

no

Technical impact

total

Assessed

21 mo ago (2025-02-04)

6.08% chance of exploitation in the next 30 days, higher than 93% of all scored CVEs (FIRST EPSS, 2026-11-08).

• Microsoft Microsoft Office 2010 Service Pack 2
• Microsoft Microsoft Office 2013 Service Pack 1
• Microsoft Microsoft Office 2016

• msrc.microsoft.com /update-guide/vulnerability/CVE-2021-27059

  vendor-advisory, patch

• portal.msrc.microsoft.com /en-US/security-guidance/advisory/CVE-2021-27059

  patch, vendor-advisory

• cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27059

  government-resource, us-government-resource

• CVE List CVE-2021-27059
• NVD CVE-2021-27059

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.