Authenticated code execution via unsafe deserialization
Published Aug 11, 2026 · Updated Aug 25, 2026
Deserialization of untrusted data in Microsoft SharePoint 2016, 2019, and Subscription Edition allows remote authenticated users to execute code. Microsoft has disclosed only the weakness class; the public record does not identify the affected SharePoint component or the specific deserialization path that reconstructs attacker-controlled data. Exploitation requires valid authentication and network reachability to a vulnerable on-premises SharePoint server, with published impact bounded to server-side code execution.
Summary
What happened
Deserialization of untrusted data in Microsoft SharePoint 2016, 2019, and Subscription Edition allows remote authenticated users to execute code. Microsoft has disclosed only the weakness class; the public record does not identify the affected SharePoint component or the specific deserialization path that reconstructs attacker-controlled data. Exploitation requires valid authentication and network reachability to a vulnerable on-premises SharePoint server, with published impact bounded to server-side code execution.
The record
- CVE
- CVE-2026-66805
- Published
- Aug 11, 2026
- Updated
- Aug 25, 2026
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-502, CAPEC-586, T1190
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 11, 2026CVE publishedPublication date reported by the CVE source.
- Aug 25, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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