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Microsoft Office Use-After-Free Remote Code Execution Vulnerability

IdentifiersCVE-2026-20952CWE-416· Use After Free

CVE-2026-20952 is a use-after-free vulnerability in Microsoft Office. Microsoft describes it as allowing an unauthorized attacker to execute code locally, and supporting reporting consistently characterizes it as a critical Office remote code execution issue. The flaw is memory-safety related and affects multiple Office product lines, including Microsoft Office LTSC for Mac 2021 and 2024, Office LTSC 2024, Office LTSC 2021, Office 2019, Office 2016, and Microsoft 365 Apps for Enterprise. Multiple sources in the provided content state that exploitation can be triggered through a crafted Office document and that the Preview Pane is a valid attack vector in some scenarios.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can result in arbitrary code execution in the context of the targeted Office application and effectively compromise the affected host. Reporting in the provided content indicates high impact to confidentiality, integrity, and availability, consistent with the listed CVSS v3.1 vector. An attacker could use the vulnerability to run malicious payloads, take control of the system in the current user context, and potentially leverage that access for further compromise.

Mitigation

If you can’t patch tonight, do this now.

Until patches are fully deployed, reduce exposure to untrusted Office content, especially documents received via email or external sources. Because the provided content states the Preview Pane is a valid attack vector, disable or avoid use of Preview Pane where operationally feasible. Harden email and document-handling workflows, block or sandbox suspicious Office files, and monitor for abnormal Office child-process execution or other post-exploitation behavior. No content-provided workaround is described as fully remediating the flaw aside from patching.

Remediation

Patch, then assume compromise.

Apply Microsoft's January 2026 security updates for all affected Microsoft Office products. The content specifically references Office 2016 update KB5002826 for MSI-based installations, while Click-to-Run and Microsoft 365 Apps for Enterprise deployments should be updated to the vendor-fixed builds delivered through their respective update channels. Ensure all affected Office LTSC, Office 2019, Office 2016, Microsoft 365 Apps for Enterprise, and listed Mac Office releases are brought to patched versions.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
Microsoft Corporation365 Appsapplication
Microsoft CorporationOfficeapplication
Microsoft CorporationOffice 2016application
Microsoft CorporationOffice 2019application
Microsoft CorporationOffice 2021application
Microsoft CorporationOffice 2024application
Microsoft CorporationOffice Long Term Servicing Channelapplication
Microsoft CorporationOffice Macos 2021application
Microsoft CorporationOffice Macos 2024application

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity4

Community discussion across Reddit, Mastodon, and other social sources.