MSRC_CVE-2026-21509
Vulnerability from csaf_microsoft - Published: 2026-01-13 08:00 - Updated: 2026-01-26 08:00Summary
Microsoft Office Security Feature Bypass Vulnerability
Notes
Additional Resources
To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle
Disclaimer
The information provided in the Microsoft Knowledge Base is provided \"as is\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.
Customer Action
Required. The vulnerability documented by this CVE requires customer action to resolve.
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"vulnerabilities": [
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"cve": "CVE-2026-21509",
"cwe": {
"id": "CWE-807",
"name": "Reliance on Untrusted Inputs in a Security Decision"
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"notes": [
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"title": "Assigning CNA"
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"category": "faq",
"text": "An attacker must send a user a malicious Office file and convince them to open it.",
"title": "According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do?"
},
{
"category": "faq",
"text": "The security update for Microsoft Office Client 2016 and 2019 versions are not immediately available. These updates will be released as soon as possible, and when they are available, customers will be notified via a revision to this CVE.",
"title": "Are the updates for the Microsoft Office Client versions currently available?"
},
{
"category": "faq",
"text": "This update addresses a vulnerability that bypasses OLE mitigations in Microsoft 365 and Microsoft Office which protect users from vulnerable COM/OLE controls.",
"title": "What kind of security feature could be bypassed by successfully exploiting this vulnerability?"
},
{
"category": "faq",
"text": "No, the Preview Pane is not an attack vector.",
"title": "Is the Preview Pane an attack vector for this vulnerability?"
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"date": "2026-01-26T08:00:00.000Z",
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"scores": [
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"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"environmentalsScore": 0.0,
"exploitCodeMaturity": "UNPROVEN",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"remediationLevel": "OFFICIAL_FIX",
"reportConfidence": "CONFIRMED",
"scope": "UNCHANGED",
"temporalScore": 6.8,
"userInteraction": "REQUIRED",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C",
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"title": "Microsoft Office Security Feature Bypass Vulnerability"
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}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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