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CVE-2026-40357 is a remote code execution vulnerability in on-premises Microsoft SharePoint Server caused by deserialization of untrusted data. SharePoint improperly processes attacker-controlled serialized input without sufficient validation, allowing an authenticated user to trigger unsafe deserialization over the network. Microsoft states that exploitation requires only low privileges, specifically a minimum of Site Member permissions, and no user interaction. The issue affects supported on-premises SharePoint product lines including SharePoint Enterprise Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition prior to the patched builds released in May 2026.
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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.
8 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A May 2026 Microsoft SharePoint remote code execution vulnerability referenced for comparison with CVE-2026-47294.
A remote code execution vulnerability in Microsoft SharePoint Server caused by insecure deserialization of untrusted data, allowing an authenticated low-privilege user to execute arbitrary code remotely.
Another SharePoint-related CVE mentioned only as part of the cumulative May 2026 update bundle; no technical details are provided in the content.
A remote code execution vulnerability in Microsoft Office SharePoint caused by deserialization of untrusted data. It allows an authenticated attacker with low privileges to execute code over the network.
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.