Microsoft SharePoint Deserialization of Untrusted Data Vulnerability

[ Why it matters ]Priority signals

• Exploited in the wild: on CISA's Known Exploited Vulnerabilities list since 2026-07-16
• EPSS: 16% chance of exploitation in the next 30 days (higher than 97% of CVEs)
• Critical severity: CVSS 9.8

[ Description ]Official description

Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.

CISA: Microsoft SharePoint contains a deserialization of untrusted data vulnerability that allows an unauthorized attacker to execute code over a network.

[ Fixes ]Fixes and patches

CISA required action (US federal deadline 19 Jul 2026): Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

• Patch on msrc.microsoft.comVendor patch or bulletin · NVD · Reference tagged 'Patch' by NVD

[ References ]References

• msrc.microsoft.com/update-guide/vulnerability/CVE-2026-58644PatchVendor Advisory
• www.cisa.gov/known-exploited-vulnerabilities-catalogUS Government Resource