High

Microsoft Office Preview Pane Use-After-Free Remote Code Execution

IdentifiersCVE-2025-30377CWE-416· Use After Free

CVE-2025-30377 is a critical remote code execution vulnerability in Microsoft Office caused by a use-after-free condition arising from improper memory pointer management. According to the provided content, the flaw occurs when Office applications, particularly Outlook, access memory after it has already been freed while processing a specially crafted malicious Office document or attachment. The vulnerability can be triggered through Outlook’s Preview Pane, where merely previewing the malicious content may dereference a freed pointer and lead to arbitrary code execution. The content identifies affected products as Microsoft 365 Apps, Office 2016 through Office 2024, and Office Online Server 2019 through 2025 prior to the May 2025 security updates.

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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 or user session. Because the flaw can be triggered via Outlook’s Preview Pane and reportedly requires minimal or no user interaction, it materially increases phishing and email-borne attack risk. An attacker could use the vulnerability to execute a malicious payload delivered in a crafted document or attachment, enabling compromise of the affected endpoint and follow-on activity such as malware deployment, persistence, data access, or lateral movement, subject to the privileges of the compromised user context.

Mitigation

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

If immediate patching is not possible, temporarily disable Outlook’s Preview Pane to reduce exposure to preview-triggered exploitation. Additionally, monitor for unusual Office process behavior with EDR tooling and inspect suspicious email attachments and Office documents through email security controls. These measures are mitigations only and do not replace vendor patching.

Remediation

Patch, then assume compromise.

Apply Microsoft’s May 2025 security updates for affected Microsoft Office products, including Microsoft 365 Apps, supported Office desktop versions, and Office Online Server. The content specifically indicates that Microsoft addressed CVE-2025-30377 in the May 2025 Patch Tuesday release and recommends immediate deployment via Windows Update or the Microsoft Update Catalog.

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 CorporationExcelapplication

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

Microsoft CorporationOffice Online Serverapplication

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

ACTIVITY FEED

Recent activity

10 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

10 SOURCESView more in app

sophos threat researchNews

Jan 1, 2026

Microsoft primes 71 fixes for May Patch Tuesday | SOPHOS

A critical remote code execution vulnerability in Microsoft Office and Microsoft 365 that can be triggered via the Preview Pane.

cso onlineNews

Dec 30, 2025

Patch Tuesday 2025 roundup: The biggest Microsoft vulnerabilities of the year

A critical vulnerability in Microsoft Office that could be exploited via the Preview Pane, allowing code execution when a specially crafted file or email is previewed.

May 14, 2025

Apple patched one first, but Microsoft’s blasted five exploited flaws this Pa-Tu

Microsoft Office remote code execution vulnerability.

cyberthroneNews

May 14, 2025

Microsoft Patch Tuesday May 2025

A remote code execution vulnerability in Microsoft Office, exploitable via the Preview Pane in Outlook.

+5 more in the timeline

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.

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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 activity1