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    CVE-2026-21509

    Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.

    Published:Jan 26, 2026
    Last Modified:Apr 22, 2026
    EPS:Jan 26, 2026
    EPSS Score:0.10862
    CVSS Score:7.8

    CISA Notification

    Description

    Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.

    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.

    Notes:

    No extra notes provided.

    Due Date
    Feb 16, 2026
    207 days ago
    Alert Date
    Jan 26, 2026
    228 days ago

    Affected Products

    Vendor
    Microsoft
    Product
    365 Apps
    Vendor
    Microsoft
    Product
    Office
    Vendor
    Microsoft
    Product
    Office 2016
    Vendor
    Microsoft
    Product
    Office 2019
    Vendor
    Microsoft
    Product
    Office 2021
    Vendor
    Microsoft
    Product
    Office 2024
    Vendor
    Microsoft
    Product
    Office Long Term Servicing Channel

    Exploits

    https://github.com/DameDode/CVE-2026-21509-POChttps://github.com/decalage2/detect_CVE-2026-21509https://github.com/gavz/CVE-2026-21509-PoChttps://github.com/kaizensecurity/CVE-2026-21509https://github.com/kimstars/Ashwesker-CVE-2026-21509https://github.com/ksk-itdk/KSK-ITDK-CVE-2026-21509-Mitigationhttps://github.com/planetoid/cve-2026-21509-mitigationhttps://github.com/razureink/cve-2026-21509-office_security_bypass_reproductionhttps://github.com/sentinel-aidefense/CVE-2026-21509https://github.com/SimoesCTT/CTT-MICROSOFT-OFFICE-OLE-MANIFOLD-BYPASS-CVE-2026-21509https://github.com/SimoesCTT/CTT-NFS-Vortex-RCEhttps://github.com/SimoesCTT/SCTT-2026-33-0007-The-OLE-Vortex-Laminar-Bypass-https://github.com/suuhm/CVE-2026-21509-handler

    Common Attack Pattern Enumeration and Classification (CAPEC)

    No CAPEC recorded yet

    Related CVEs

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    CVE-2026-83949 (CVSS 5.5) — Buffer over-read in Microsoft Office Word allows an unauthorized attacker to disclose information locally.…
    CVE-2026-83951 (CVSS 5.5) — Buffer over-read in Microsoft Office Word allows an unauthorized attacker to disclose information locally.…
    CVE-2026-81948 (CVSS 7.8) — Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.…
    CVE-2026-81950 (CVSS 7.8) — Double free in Microsoft Office Excel allows an unauthorized attacker to execute code locally.…
    CVE-2026-81949 (CVSS 7.8) — Integer overflow or wraparound in Microsoft Office Excel allows an unauthorized attacker to execute code local…
    CVE-2026-81953 (CVSS 7.8) — Stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.…
    CVE-2026-81959 (CVSS 7.8) — Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.…
    CVE-2026-81952 (CVSS 8.8) — Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a net…

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High