Microsoft has released emergency out-of-band security updates to patch a high-severity Microsoft Office zero-day vulnerability exploited in attacks.
The security feature bypass vulnerability, tracked as
CVE-2026-21509,
affects multiple Office versions, including Microsoft Office 2016, Microsoft Office 2019, Microsoft Office LTSC 2021, Microsoft Office LTSC 2024, and Microsoft 365 Apps for Enterprise (the company's cloud-based subscription service).
However, as noted in today's advisory, security updates for Microsoft Office 2016 and 2019 are
not yet available and will be released as soon as possible.
While the preview pane is not an attack vector, unauthenticated local attackers can still successfully exploit the vulnerability through low-complexity attacks that require user interaction.
Microsoft has released emergency security updates to patch a high-severity Office zero-day vulnerability exploited in attacks.
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