Microsoft Office Security Feature Bypass Vulnerability

Technical Severity

CVSS v3.1 Metrics

HIGH

7.8 / 10

Minimal Risk Critical

Vector Specification

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Exploitation Likelihood

EPSS Prediction

2.91 %

Predictive Probability

Percentile Rank

86.0 th

Documented as more likely to be exploited than 86.0% of known CVEs.

Detection Date

Jan 26, 2026

Remediation Due

Feb 16, 2026

CISA Catalog Active

Threat Analysis

Microsoft Office contains a security feature bypass vulnerability in which reliance on untrusted inputs in a security decision in Microsoft Office could allow an unauthorized attacker to bypass a security feature locally. Some of the impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version.

Remediation Directive

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Asset Context

Vendor Identity

Microsoft

Affected Product

Office

Ransomware Status

Campaign Use Unknown

Weakness Classification

CWE-807

External Intelligence

Please adhere to Microsoft’s recommended guidelines to address this vulnerability. Implement all final mitigations provided by the vendor for Office 2021, and apply the interim corresponding mitigations for Office 2016 and Office 2019 until the final patch becomes available. For more information please see:

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509

NVD

National Vulnerability Database

https://nvd.nist.gov/vuln/detail/CVE-2026-21509