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CVE-2026-55140 is a heap-based buffer overflow vulnerability in Microsoft Office. The flaw can be triggered when Microsoft Office processes a specially crafted malicious document, including through direct opening of the file or rendering via the Preview Pane. Successful exploitation allows unauthorized code execution in the security context of the affected local user or system handling the document. The vulnerability is classified as a remote code execution issue because attacker-controlled content can cause memory corruption during document parsing or rendering, leading to execution of arbitrary code.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
1 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
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.