US EditionOffice Zero-Day Exploited, Forces Microsoft OOB Patch
Microsoft patched a high-severity Office zero-day exploited via low-complexity local attacks that bypass OLE mitigations, but updates for Office 2016 and 2019 are pending.
- On Monday, Microsoft disclosed CVE-2026-21509 and released emergency out-of-band updates rolling out for Microsoft 365 Apps for Enterprise and multiple Microsoft Office LTSC and perpetual releases.
- The flaw bypasses Object Linking and Embedding and COM mitigations, enabling attackers to exploit phishing-style, user-interaction attacks with circulating exploit code, Microsoft said.
- Microsoft published Registry mitigation steps to create a COM Compatibility key and set a Compatibility Flags value to 400; Office 2021 and later get auto-protection after restart, but patches for Microsoft Office 2016 and 2019 are pending.
- Close all Microsoft Office applications before editing the Windows Registry, back up the Registry to avoid system issues, and after performing the steps, the flaw is mitigated on next Office launch.
- Earlier this month, as part of the January 2026 Patch Tuesday, Microsoft fixed 114 flaws including an actively exploited Desktop Window Manager zero-day, and last week it issued other out-of-band fixes while declining to name the vulnerability's discoverer.
13 Articles
13 Articles
Microsoft recently published a security advisory warning of a newly discovered zero-day vulnerability in Office applications. This vulnerability, designated CVE-2026-21509, is rated as "high" risk. According to official information, the flaw can be exploited to bypass security features in various Office versions, including Microsoft Office 2016, 2019, 2021 LTSC, and 2024 LTSC. Users are therefore urged to install the emergency patches provided b…
Microsoft has patched the CVE-2026-21509 vulnerability, which appears to have already been exploited in targeted attacks. Several Office versions are affected. The software group has released security updates for the zero-day gap CVE-2026-21509, which allows attackers to bypass security mechanisms in Office. According to the company's security advice, the vulnerability has already been actively exploited. Discovery by Microsoft researchers thems…
Coverage Details
Bias Distribution
- 67% of the sources are Center
Factuality
To view factuality data please Upgrade to Premium
