Microsoft Office Use-After-Free Remote Code Execution Vulnerability
CVE-2026-40358 is a critical use-after-free vulnerability in Microsoft Office. Microsoft classifies the issue as CWE-416 and states that the flaw allows an unauthorized attacker to execute code locally. Although the vulnerability is titled as a remote code execution issue, the supporting advisory content clarifies that the attack vector is local and that the Preview Pane can be used as an attack vector. The available information indicates exploitation occurs when Office processes specially crafted content, leading to a use-after-free condition that can be leveraged for code execution.
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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 use-after-free vulnerability in Microsoft Office that allows local code execution.
A critical use-after-free remote code execution vulnerability in Microsoft Office that allows an unauthorized attacker to execute code locally, including via the Preview Pane attack vector.
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.