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CVE-2026-26109 is an Important vulnerability in Microsoft Office Excel caused by an out-of-bounds read. The flaw allows an unauthorized attacker to achieve local code execution. Available reporting identifies the weakness as CWE-125 and describes the issue as occurring within Excel when processing crafted input that can trigger memory access beyond intended bounds. Specific vulnerable functions or parsing components have not been publicly detailed in the available information.
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What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
If you can’t patch tonight, do this now.
Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
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.
6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An out-of-bounds read vulnerability in Microsoft Excel that could lead to local code execution and system compromise.
An out-of-bounds read vulnerability in Microsoft Office Excel that can lead to local code execution.
An important Microsoft Office Excel remote code execution vulnerability caused by an out-of-bounds read that could allow local code execution.
A notable Microsoft Office / 365 Apps / Teams vulnerability in a cluster of RCE, EoP, and information disclosure issues with broad enterprise exposure.
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.