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CVE-2026-40363 is a critical heap-based buffer overflow in Microsoft Office. Microsoft classifies the issue as a remote code execution vulnerability, while describing exploitation as local code execution by an unauthorized attacker. Available information indicates that malformed Office content can trigger memory corruption in Office, leading to out-of-bounds writes on the heap and subsequent arbitrary code execution. The Preview Pane is identified as a viable attack vector, indicating that exploitation may occur during content rendering rather than requiring full document editing or explicit opening in all cases. Microsoft maps the flaw to CWE-122.
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No public exploit code observed for this vulnerability.
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7 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.
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.