CVE-2026-20963
Microsoft SharePoint Deserialization of Untrusted Data Vulnerability
Microsoft SharePoint
Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 18 March 2026. US federal agencies were required to remediate it by 21 March 2026.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 29.2%, which is higher than 98.2% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Frequently asked questions
Is CVE-2026-20963 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2026-20963.
What does CVE-2026-20963 affect?
CVE-2026-20963 affects Microsoft SharePoint. Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.
How severe is CVE-2026-20963?
CVE-2026-20963 is rated CRITICAL with a CVSS base score of 9.8. EPSS puts the probability of exploitation in the next 30 days at 29.2%, higher than 98.2% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 21 March 2026.
How should organisations respond to CVE-2026-20963?
Apply the vendor patch for Microsoft SharePoint as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.