Microsoft Office Zero-Day (CVE-2026-21509) - Emergency Patch Issued for Active Exploitation

The Hacker News·Jan 27

✦ NabkaNews BriefAuto-summarized from multiple outlets · verify with the source

A zero-day vulnerability in Microsoft Office, identified as CVE-2026-21509, is being actively exploited. Microsoft has issued an emergency patch to address the issue. However, reports suggest that exploitation may be continuing, with some outlets indicating that attackers, possibly including russian hackers, are still taking advantage of the vulnerability despite the emergency patch.

Full coverage

CVE-2026-21509: Actively Exploited Microsoft Office Zero-Day Forces Emergency Patch

SOC Prime·Jan 27

Microsoft reveals actively exploited Office zero-day, provides emergency fix (CVE-2026-21509)

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Redmondmag.com·Feb 4

Microsoft Office CVE-2026-21509 Zero-Day: Emergency Patch Released to Counter Active Exploitation

Rescana·Jan 28

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