Microsoft Office Heap-Based Buffer Overflow Remote Code Execution Vulnerability
CVE-2026-40363 is a critical heap-based buffer overflow in Microsoft Office. Microsoft classifies it as a remote code execution vulnerability, while specifying that exploitation occurs through a local attack vector. The available reporting indicates that the flaw can be triggered through Office content and that the Preview Pane is an attack vector. Successful exploitation allows an unauthorized attacker to execute code locally. Microsoft assigned CVSS v3.1 AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H with a base score of 8.4. The specific vulnerable function or code path is not provided in the supplied content.
Are you exposed to this one?
Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.
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.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
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.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Microsoft Office remote code execution vulnerability that can be exploited via the Preview Pane.
A Microsoft Office remote code execution vulnerability that can be exploited via the Preview Pane.
A critical heap-based buffer overflow vulnerability in Microsoft Office that allows local code execution.
A critical heap-based buffer overflow vulnerability in Microsoft Office that allows unauthorized local code execution and is described by Microsoft as a remote code execution vulnerability due to the attacker’s location.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.