How severe is CVE-2021-27059?

CVE-2021-27059 has a CVSS score of 7.6/10, rated HIGH. Immediate patching is strongly recommended.

Which products are affected by CVE-2021-27059?

CVE-2021-27059 affects the following products: microsoft office, microsoft office 2016.

How do I patch CVE-2021-27059?

No patch has shipped for CVE-2021-27059 yet — track the microsoft office advisory for a fixed release and apply the workarounds below in the meantime.

How do I detect CVE-2021-27059 across my infrastructure?

Inventory every microsoft office deployment and check each version against the affected-products list above.

How do I mitigate CVE-2021-27059 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.

Is CVE-2021-27059 actively exploited in the wild?

Yes. There are 2 known exploit references for CVE-2021-27059, including 2 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-27059?

CVE-2021-27059 has an EPSS (Exploit Prediction Scoring System) score of 6.1%, placing it in the 93th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

Is CVE-2021-27059 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-27059 (Microsoft Office Remote Code Execution Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03. CISA required all US federal civilian agencies to remediate this vulnerability by 2021-11-17. The required action was: Apply updates per vendor instructions. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

Which products and versions are affected by CVE-2021-27059?

CVE-2021-27059 affects microsoft office (2 versions, e.g. 2010, 2013); microsoft office 2016. Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2021-27059 published, and has it been updated?

CVE-2021-27059 was published on March 11, 2021 and was last updated on August 19, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🛡️

CISA KEV · ACTIVELY EXPLOITED

HIGH severity

CVE-2021-27059 — OFFICE

HIGH

CVE-2021-27059 is a high-severity (CVSS 7.6) remote code execution vulnerability in microsoft office. It is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

Microsoft Office Remote Code Execution Vulnerability

Published

Mar 11, 2021

Updated

Aug 19, 2026

Affected

2 products

Patched

See advisory

Exploits

2 known

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2021-11-03. Federal agencies were required to remediate by 2021-11-17.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-27059.

EPSS Exploitation Probability

via FIRST.org ↗

6.1%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs93th percentile — riskier than 93% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-27059 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Description

Microsoft Office Remote Code Execution Vulnerability

Affected Products

2 products · 5 configurations

Application

officemicrosoft

2 versions

20102013

Application

office 2016microsoft

all

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Microsoft Office Remote Code Execution Vulnerability

portal.msrc.microsoft.comMSMar 2021

Microsoft Office Remote Code Execution Vulnerability

cisa.govCISANov 2021

Detection & mitigation playbook

Vendor / appliance

Detect
Inventory every microsoft office deployment and check each version against the affected-products list above.
Remediation status
No patch has shipped for CVE-2021-27059 yet — track the microsoft office advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.

Frequently Asked Questions

Microsoft Office Remote Code Execution Vulnerability

O3 Security · Runtime Protection

Is CVE-2021-27059 being exploited in your environment?

Detect and block the exploit chain at execution, on systems you cannot patch yet.

Protect my workloads How runtime protection works

CVE-2021-27059 — OFFICE

Exploitation Status

Actively exploited in the wild

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Description

Affected Products

Detection & mitigation playbook

Detect

Remediation status

Mitigate without a patch

Frequently Asked Questions

Is CVE-2021-27059 being exploited in your environment?