CVE-2025-53770: in the CISA KEV catalogue
Microsoft SharePoint Deserialization of Untrusted Data Vulnerability. CISA added CVE-2025-53770 to the Known Exploited Vulnerabilities catalogue on 2025-07-20 with a default due date of 2025-07-21. Known ransomware campaign use: Known. Forensic triage flag: No.
Microsoft SharePoint Server on-premises contains a deserialization of untrusted data vulnerability that could allow an unauthorized attacker to execute code over a network. This vulnerability could be chained with CVE-2025-53771. CVE-2025-53770 is a patch bypass for CVE-2025-49704, and the updates for CVE-2025-53770 include more robust protection than those for CVE-2025-49704. (CISA description)
- Vendor / product
- Microsoft SharePoint
- CWE
- CWE-502
- CISA required action
- Disconnect public-facing versions of SharePoint Server that have reached their end-of-life (EOL) or end-of-service (EOS) to include SharePoint Server 2013 and earlier versions. For supported versions, please follow the mitigations according to CISA (URL listed below in Notes) and vendor instructions (URL listed below in Notes). Adhere to the applicable BOD 22-01 guidance for cloud services or discontinue use of the product if mitigations are not available.
- EPSS
- 100%, percentile 99 (scored 2026-11-03)
EPSS puts nearly every time in 100 odds (100%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 99% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.
Vendor and reference links (from CISA)
- 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
- https://nvd.nist.gov/vuln/detail/CVE-2025-53770
Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.
Frequently asked questions
Is CVE-2025-53770 in the CISA KEV catalogue?
Yes. CISA added CVE-2025-53770 (Microsoft SharePoint Deserialization of Untrusted Data Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2025-07-20. CISA's default due date for it is 2025-07-21.
Is CVE-2025-53770 used in ransomware attacks?
CISA marks known ransomware campaign use as Known for CVE-2025-53770.
What should I do about CVE-2025-53770?
CISA's required action: Disconnect public-facing versions of SharePoint Server that have reached their end-of-life (EOL) or end-of-service (EOS) to include SharePoint Server 2013 and earlier versions. For supported versions, please follow the mitigations according to CISA (URL listed below in Notes) and vendor instructions (URL listed below in Notes). Adhere to the applicable BOD 22-01 guidance for cloud services or discontinue use of the product if mitigations are not available.
Sources
- CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
- FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
- NVD record for CVE-2025-53770