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CVE-2026-63520 is an improper input validation vulnerability in Microsoft SharePoint Server Business Connectivity Services (BCS). The vulnerable DbTypeReflector.ResolveDotNetType method resolves attacker-controlled assembly-qualified .NET type names supplied through a Business Data Connectivity model without adequately restricting allowed types. Subsequent BCS processing can instantiate resolved types and set attacker-controlled properties, enabling exploitation through available deserialization or object-instantiation gadget chains. Microsoft addressed the issue in August 2026 updates for supported on-premises SharePoint Server releases. SharePoint Online is not affected.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos (1 hidden).
The repository contains a README and one standalone Python exploit, poc.py; it is not a Metasploit, Nuclei, or other framework module. The script implements a claimed unauthenticated SharePoint RCE chain against CVE-2026-55040 and CVE-2026-63520. First, it requests public SharePoint STS metadata to recover the token realm and calculate an x5t value from the advertised signing certificate. It also performs optional NTLM and TLS-certificate reconnaissance to identify target naming information. It then constructs nested JWTs: an unsigned outer token (alg:none) that carries a selected user identity and an inner RS256-formatted actor token with a non-empty dummy signature and the recovered x5t. The README and code identify SID, UPN, and limited AccessToken identity modes; optional impacket-assisted domain-SID discovery is available through --domain-ip. After confirming access, the script generates a malicious BDCM XML model, creates a BusinessDataMetadataCatalog location, uploads the model, refreshes SharePoint request digests, and invokes ProcessQuery to cause BDC unsafe type resolution. The intended gadget is System.Windows.Data.ObjectDataProvider, configured to call Process.Start on a user-controlled executable and argument string. This yields arbitrary command execution under the SharePoint service/application-pool identity. The command is configurable through --cmd, while --check-only stops after authentication-bypass validation.
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101 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A vulnerability affecting Microsoft SharePoint Server that open-source reporting indicates is actively exploited in the wild.
A Microsoft SharePoint Business Connectivity Services vulnerability that can be chained with CVE-2026-55040 to obtain remote code execution. A public PoC is available, and the chain has been probed in honeypots, but the content reports no observed code execution and Microsoft had not classified this CVE as exploited in the wild.
A high-severity SharePoint Server remote-code-execution vulnerability in Business Connectivity Services. Insufficient restrictions on .NET types in Business Data Connectivity models enable authenticated attackers to submit a malicious BDC model and abuse a LosFormatter deserialization gadget for arbitrary server-side code execution. It is exploitable in a chain following the CVE-2026-55040 authentication bypass.
An unsafe .NET type instantiation vulnerability in Microsoft SharePoint Business Connectivity Services that can be used for remote code execution when chained with authentication bypass.
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Cross-references every affected SKU, including bundled OEM variants.
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