CERT-EU issued an urgent security advisory regarding CVE-2026-20963, a critical unauthenticated remote code execution vulnerability in Microsoft SharePoint caused by the deserialization of untrusted data. The flaw is actively being exploited in the wild, prompting strong recommendations to immediately patch internet-facing servers, enable AMSI, and rotate ASP.NET machine keys.
CVE-2026-20963
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Security Advisory 2026-004 CISA Adds One Known Exploited Vulnerability to Catalog CISA has added CVE-2026-20963, a Microsoft SharePoint Deserialization of Untrusted Data Vulnerability, to its Known Exploited Vulnerabilities (KEV) Catalog due to evidence of active exploitation. Organizations are strongly urged to prioritize timely remediation of this flaw as part of their vulnerability management practices to reduce exposure to cyberattacks.