Authenticated code execution via unvalidated proxy namespace
Published May 9, 2023 · Updated Oct 21, 2025
Code injection in Microsoft SharePoint Server allows remote authenticated users with Site Owner privileges to execute arbitrary code. The DynamicProxyGenerator.GenerateProxyAssembly method accepts an unvalidated WebServiceProxyNamespace value from writable BDC metadata, emits it as C# source, compiles the resulting assembly, and instantiates its injected type. Site Owner privileges are normally required; a separate SharePoint authentication bypass can remove that gate, after which code runs as the farm service account.
Summary
What happened
Code injection in Microsoft SharePoint Server allows remote authenticated users with Site Owner privileges to execute arbitrary code. The DynamicProxyGenerator.GenerateProxyAssembly method accepts an unvalidated WebServiceProxyNamespace value from writable BDC metadata, emits it as C# source, compiles the resulting assembly, and instantiates its injected type. Site Owner privileges are normally required; a separate SharePoint authentication bypass can remove that gate, after which code runs as the farm service account.
The record
- CVE
- CVE-2023-24955
- Published
- May 9, 2023
- Updated
- Oct 21, 2025
- Vendor
- Microsoft
- Product
- Microsoft SharePoint Enterprise Server 2016
- Classifications
- CWE-94, T1190
- Attack vector
- network
- Privileges
- admin
Timeline
How it unfolded
- May 9, 2023CVE publishedPublication date reported by the CVE source.
- Oct 21, 2025Record updatedLatest update available in the CVE record.
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 <16.0.5395.1000
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
- STAR Labs SharePoint pre-auth RCE chain demonstrationfunctional · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- CISA Known Exploited Vulnerabilities listingknown exploited catalog
- CISA ransomware campaign associationransomware
Technologies
Your stack
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Your stack
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