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01 Record

CVE-2026-21509

Microsoft Office Security Feature Bypass Vulnerability

HighKEVPUBLISHEDCNA: microsoft
CNA base score7.8 CVSS v3.xCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
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02 Description

Microsoft Office Security Feature Bypass Vulnerability

03 Exploitation and scoring

Exploitation
Exploited in the wild. Listed in the CISA Known Exploited Vulnerabilities catalog on 2026-01-26. Federal remediation due 2026-02-16.
SSVC decision
  • ExploitationactiveCISA reports credible evidence of active exploitation.
  • AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
  • Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
70.79% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 99.3% of scored records. A rank, not a probability.
NVD base score
7.8 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD analysis status
Analyzed. NVD last modified this record on 2026-06-25.
Red Hat severity
No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2026-01-26 17:06Z9 MO AGO
Last updated
2026-07-30 20:47Z3 MO AGO
Reserved
2025-12-30
Assigning CNA
microsoft
Record state
PUBLISHED
Severity
High (CVSS 7.8)
CNA CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
Weaknesses
  • CWE-807Reliance on Untrusted Inputs in a Security DecisionBase
Data version
5.2
Document digest
2a09fd35bec50b8a455a8b4dcc9d6d5d4208eeffa6dfe208e1d53ef0bf9db757

05 Affected products

VendorProductVersionsPlatforms
MicrosoftMicrosoft 365 Apps for Enterprise16.0.1 to < https://aka.ms/OfficeSecurityReleases32-bit Systems, x64-based Systems
MicrosoftMicrosoft Office 201616.0.0 to < 16.0.5539.100132-bit Systems, x64-based Systems
MicrosoftMicrosoft Office 201919.0.0 to < 16.0.10417.2009532-bit Systems, x64-based Systems
MicrosoftMicrosoft Office LTSC 202116.0.1 to < https://aka.ms/OfficeSecurityReleases32-bit Systems, x64-based Systems
MicrosoftMicrosoft Office LTSC 202416.0.0 to < https://aka.ms/OfficeSecurityReleases32-bit Systems, x64-based Systems

06 References