CVE-2025-53770: Microsoft SharePoint Deserialization of Untrusted Data Vulnerability

How to check if you are exposed to CVE-2025-53770

1. Find every Microsoft SharePoint system you or your clients run, including ones exposed to the internet. Those come first: CISA only lists flaws attackers are already using.
2. Compare each version with the fixed versions in the vendor advisory below. Where no fix exists yet, apply the vendor’s mitigation or take the system off the internet.
3. Run a credentialed vulnerability scan to catch the systems you missed, then check that the next scan no longer reports CVE-2025-53770.

US federal agencies had to fix this by 2025-07-21. Everyone else should treat that deadline as a guide: if it has passed, this is overdue.

Timeline

1. 2025-07-20 · Added to CISA's Known Exploited Vulnerabilities catalog
2. 2025-07-21 · Fix-by date for US federal agencies, passed 468 days ago

Vendor advisories and fixes

• https://www.cisa.gov/news-events/alerts/2025/07/20/microsoft-releases-guidance-exploitation-sharepoint-vulnerability-cve-2025-53770
• https://www.microsoft.com/en-us/security/blog/2025/07/22/disrupting-active-exploitation-of-on-premises-sharepoint-vulnerabilities/
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-53770

Weakness type

• CWE-502

More exploited Microsoft vulnerabilities

CISA lists 390 exploited Microsoft vulnerabilities. The closest matches:

• CVE-2026-65660Microsoft SharePoint Code Injection VulnerabilityAdded 2026-09-25
• CVE-2026-55040Microsoft SharePoint Weak Authentication VulnerabilityAdded 2026-08-18
• CVE-2026-50522Microsoft SharePoint Deserialization of Untrusted Data Vulnerability Added 2026-07-22
• CVE-2026-58644Microsoft SharePoint Deserialization of Untrusted Data VulnerabilityAdded 2026-07-16
• CVE-2026-20963Microsoft SharePoint Deserialization of Untrusted Data VulnerabilityAdded 2026-03-18
• CVE-2025-49706Microsoft SharePoint Improper Authentication VulnerabilityAdded 2025-07-22
• CVE-2025-49704Microsoft SharePoint Code Injection VulnerabilityAdded 2025-07-22
• CVE-2024-38094Microsoft SharePoint Deserialization VulnerabilityAdded 2024-10-22

Keep going

• All exploited CVEs
• Check another CVE
• What is CISA KEV?
• What is EPSS?

Sources: CISA Known Exploited Vulnerabilities catalog (version 2026.10.30); EPSS data from FIRST.org; CVSS and descriptions from the NIST National Vulnerability Database. Checked 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.