Unauthenticated code execution via unsafe deserialization
Published Jan 13, 2026 · Updated Jan 13, 2026
Unsafe deserialization in affected Microsoft SharePoint Server 2016, 2019, and Subscription Edition builds allows remote attackers to execute code. Microsoft has not disclosed the deserialization locus or the wrong operation beyond accepting untrusted serialized data. No authentication or user interaction is required, and successful exploitation provides code execution in the SharePoint server context.
Summary
What happened
Unsafe deserialization in affected Microsoft SharePoint Server 2016, 2019, and Subscription Edition builds allows remote attackers to execute code. Microsoft has not disclosed the deserialization locus or the wrong operation beyond accepting untrusted serialized data. No authentication or user interaction is required, and successful exploitation provides code execution in the SharePoint server context.
The record
- CVE
- CVE-2026-20963
- Published
- Jan 13, 2026
- Updated
- Jan 13, 2026
- Vendor
- Microsoft
- Product
- Microsoft SharePoint Enterprise Server 2016
- Classifications
- CWE-502, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 13, 2026CVE publishedPublication date reported by the CVE source.
- Jan 13, 2026Record updatedLatest update available in the CVE record.
- Mar 18, 2026Exploitation reportedCISA Known Exploited Vulnerabilities Catalog listing
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 <16.0.5535.1001
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 listingknown exploited catalog
Technologies
Your stack
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Your stack
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