CVE-2026-58644
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 16 July 2026. US federal agencies were required to remediate it by 19 July 2026.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 15.9%, which is higher than 96.9% 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-2026-58644 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2026-58644.
What does CVE-2026-58644 affect?
CVE-2026-58644 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-2026-58644?
CVE-2026-58644 is rated CRITICAL with a CVSS base score of 9.8. EPSS puts the probability of exploitation in the next 30 days at 15.9%, higher than 96.9% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 19 July 2026.
How should organisations respond to CVE-2026-58644?
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.