A critical ViewState deserialization vulnerability (CVE-2026-5426) in the KnowledgeDeliver LMS allows unauthenticated remote code execution due to shared ASP.NET machine keys across deployments. Threat actors are actively exploiting this flaw to deploy the BLUEBEAM in-memory web shell and modify application JavaScript, ultimately distributing targeted Cobalt Strike BEACON payloads to end-users visiting the compromised sites.
ViewState Deserialization
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Exploitation of KnowledgeDeliver via ViewState Deserialization Vulnerability