Authenticated code execution via unsafe deserialization
Published May 22, 2026 · Updated May 22, 2026
Deserialization of untrusted data in Microsoft SharePoint Server allows remote authenticated users to execute code over a network. Microsoft identifies unsafe deserialization as the flaw but has not disclosed the affected endpoint, serialized type, or deserialization call. A low-privileged SharePoint account can submit a crafted serialized payload and gain code execution in the server process, enabling system compromise.
Summary
What happened
Deserialization of untrusted data in Microsoft SharePoint Server allows remote authenticated users to execute code over a network. Microsoft identifies unsafe deserialization as the flaw but has not disclosed the affected endpoint, serialized type, or deserialization call. A low-privileged SharePoint account can submit a crafted serialized payload and gain code execution in the server process, enabling system compromise.
The record
- CVE
- CVE-2026-45659
- Published
- May 22, 2026
- Updated
- May 22, 2026
- Vendor
- Microsoft
- Product
- Microsoft SharePoint Enterprise Server 2016
- Classifications
- CWE-502, T1190
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- May 22, 2026CVE publishedPublication date reported by the CVE source.
- May 22, 2026Record updatedLatest update available in the CVE record.
- Jul 1, 2026Exploitation reportedCISA Known Exploited Vulnerabilities Catalog entry for CVE-2026-45659
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=16.0.0 <16.0.5552.1002
What conditions does exploitation require?
What is affected?
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.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- CISA Known Exploited Vulnerabilities Catalog entry for CVE-2026-45659known exploited catalog
Technologies
Your stack
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Your stack
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