CVE-2026-44824: Microsoft Office Heap Buffer Overflow Remote Code Execution

Technical summary

CVE-2026-44824 is a heap-based buffer overflow (CWE-122) in Microsoft Office that permits arbitrary code execution with local attack scope. The vulnerability is triggered when a user opens a malicious document; no prior authentication or special privileges are required. The CVSS 3.1 vector CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H indicates low complexity and high impact across confidentiality, integrity, and availability. The attack vector is local, meaning the threat actor must rely on social engineering or document delivery to initiate the attack.

Business impact

Organizations using Microsoft Office across their enterprise face a material risk of data exfiltration, system compromise, and potential lateral movement if employees open crafted documents delivered via email or other channels. The vulnerability affects productivity tools relied on across most business operations, making incident response and remediation operationally complex. Depending on how documents are sourced and validated within your organization, this could enable insider threats or sophisticated phishing campaigns.

Affected systems

The vulnerability impacts a broad range of Microsoft Office products and related services: Microsoft 365 Apps, Microsoft 365, Office 2016, Office 2019, Office 2021, Office 2024, and SharePoint Server. Organizations running any of these versions should assume potential exposure and prioritize inventory and patch planning accordingly.

Exploitability

While the vulnerability requires user interaction (opening a document), it does not require prior authentication or elevated privileges, lowering the barrier to exploitation. The attack complexity is low. As of the published date, this vulnerability is not listed on CISA's Known Exploited Vulnerabilities (KEV) catalog, suggesting active exploitation in the wild has not yet been publicly documented or claimed. However, the high CVSS score and ease of weaponization mean threat actors are likely developing or refining exploits.

Remediation

Microsoft has released security updates addressing this vulnerability. Organizations should apply patches to all affected Office installations as a priority. Verify patch availability and version requirements directly against Microsoft's official security advisory to ensure accurate deployment guidance for your environment. In the interim, consider restricting external document sources, implementing application whitelisting for Office, and educating users about risks of opening unexpected documents.

Patch guidance

Contact Microsoft Security Response Center or your organization's Microsoft account for definitive patch guidance. Patches should be applied to Microsoft 365 Apps, Office 2016, Office 2019, Office 2021, Office 2024, and SharePoint Server installations. Verify the specific patch version and KB article number via the official Microsoft security bulletin before deployment. Test patches in a non-production environment first to ensure compatibility with your deployed Office configurations and dependent systems.

Detection guidance

Monitor for Office process crashes or unexpected process execution chains originating from document-opening activities. Implement file integrity monitoring for Office application binaries to detect unauthorized modifications. Log document access and quarantine suspicious files (.doc, .docx, .xls, .xlsx, .ppt, .pptx) from external sources. Endpoint Detection and Response (EDR) tools should flag heap corruption attempts and anomalous memory access patterns during Office document parsing. Consider blocking or sandboxing Office documents from untrusted senders at the email gateway.

Why prioritize this

This vulnerability merits urgent attention due to its high CVSS score (7.8), complete impact on system confidentiality and integrity, low attack complexity, and the ubiquity of Microsoft Office in enterprise environments. The reliance on user interaction (rather than complete remoteness) should not diminish urgency—social engineering to deliver malicious documents is tactically simple and scalable. The absence from the KEV catalog indicates a window to patch before widespread exploitation becomes documented.

Risk score, explained

The CVSS 3.1 score of 7.8 (HIGH) reflects a local attack vector with no authentication required, requiring only user interaction. The impact ratings across all three categories (confidentiality, integrity, availability) are all High, indicating that a successful exploit results in total system compromise. The low attack complexity means no special conditions or advanced techniques are needed to trigger the flaw once a malicious document reaches a target.

Frequently asked questions