CVE-2026-21509

Known Exploited Vulnerability Entry External Catalog

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Entry Details

CVE-2026-21509

Confirmed

Yes

2026-01-26 00:00 UTC

Timestamps

2026-01-26

2026-01-26

Scope

KEV entry: Microsoft Office Security Feature Bypass Vulnerability | Affected: Microsoft / Office | Description: 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. | Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. | Due date: 2026-02-16 | Known ransomware campaign use (KEV): Unknown | Notes (KEV): 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 ; https://nvd.nist.gov/vuln/detail/CVE-2026-21509

References
  • {'id': 'CVE-2026-21509', 'url': 'https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-21509'}

f7b20c53-4e73-4ca8-8db3-73c6fc7648c1

405284c2-e461-4670-8979-7fd2c9755a60

2026-02-02 12:25 UTC

2026-02-02 12:25 UTC

Evidence (1)
Type Source Signal Confidence Details GCVE Metadata
vendor_report cisa-kev successful_exploitation 0.80
View details 
{
  "cwes": [
    "CWE-807"
  ],
  "date_added": "2026-01-26",
  "due_date": "2026-02-16",
  "feed": "CISA Known Exploited Vulnerabilities Catalog",
  "knownRansomwareCampaignUse": "Unknown",
  "product": "Office",
  "vendorProject": "Microsoft",
  "vulnerabilityName": "Microsoft Office Security Feature Bypass Vulnerability"
}
 -
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