Microsoft SharePoint Server (2016, 2019, Subscription Edition <= 2026.3.1) contains a remote code execution vulnerability in the WS-Federation passive sign-in endpoint (/_trust/default.aspx). The SharePoint authentication module (SPFederationAuthenticationModuleV2) uses a deflate-only DeflateCookieTransform (no MAC/signature check) to decode and BinaryFormatter to deserialize the SecurityContextToken Cookie value in the wresult parameter without type restrictions. An unauthenticated attacker can send a crafted WS-Federation token containing a BinaryFormatter gadget chain (DataSet + LosFormatter + XamlAssemblyLoadFromFile) to execute arbitrary code in the context of the IIS application pool identity (w3wp.exe). The fix (KB5002882, July 2026 CU) replaces the DeflateCookieTransform with
NotSupportedCookieTransform, making ReadToken() throw before deserialization.
登录后查看神龙缓存的 POC 文件快照
登录查看