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CVE-2026-40366 is a critical use-after-free vulnerability in Microsoft Office Word. The flaw occurs when Word accesses memory after it has been freed, creating a condition that can be leveraged to corrupt program state and redirect execution flow. Microsoft classifies the issue as a remote code execution vulnerability, although the published assessment indicates exploitation is carried out locally on the target machine. The vulnerability can be triggered through Word content handling, and the Preview Pane is identified as a viable attack vector.
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What an attacker gets, and what they’ve been doing with it.
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No public exploit code observed for this vulnerability.
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.
7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Microsoft Word remote code execution vulnerability that can be exploited via the Preview Pane.
A Microsoft Word remote code execution vulnerability that can be exploited via the Preview Pane.
A critical use-after-free vulnerability in Microsoft Word that allows local code execution.
A critical use-after-free remote code execution vulnerability in Microsoft Office Word that allows an unauthorized attacker to execute code locally, including via the Preview Pane attack vector.
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.