Code execution via unsafe .NET instantiation
Published Aug 11, 2026 · Updated Aug 25, 2026
Remote code execution in SharePoint Server 2016, SharePoint Server 2019, and Subscription Edition allows attackers to execute code via crafted network input. Rapid7 reports that Business Connectivity Services unsafely instantiates attacker-controlled .NET types, enabling a crafted gadget chain to run attacker-controlled OS commands as the SharePoint Site service account. Microsoft scores the flaw as reachable with no prior privileges, while Rapid7 states unauthenticated reachability in practice is achieved by chaining CVE-2026-55040; otherwise access to the vulnerable functionality is still required.
Summary
What happened
Remote code execution in SharePoint Server 2016, SharePoint Server 2019, and Subscription Edition allows attackers to execute code via crafted network input. Rapid7 reports that Business Connectivity Services unsafely instantiates attacker-controlled .NET types, enabling a crafted gadget chain to run attacker-controlled OS commands as the SharePoint Site service account. Microsoft scores the flaw as reachable with no prior privileges, while Rapid7 states unauthenticated reachability in practice is achieved by chaining CVE-2026-55040; otherwise access to the vulnerable functionality is still required.
The record
- CVE
- CVE-2026-63520
- Published
- Aug 11, 2026
- Updated
- Aug 25, 2026
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-20, T1190
- Attack vector
- network
- Privileges
- unauthenticated
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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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.
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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