CISA Adds Exploited SharePoint RCE Zero-Day CVE-2026-58644 to KEV

CISA has added a recently patched vulnerability in Microsoft SharePoint Server to its Known Exploited Vulnerabilities catalog. The vulnerability, identified as CVE-2026-58644, has a CVSS score of 9.8 and is considered critical. It is a deserialization issue that can be exploited for remote code execution. Federal Civilian Executive Branch agencies are required to apply the necessary fixes by July 19, 2026. The addition to the KEV catalog indicates that the vulnerability is being actively exploited.