CVE-2025-53770: Used in ransomware campaigns — CISA KEV

Deserialization of untrusted data in on-premises Microsoft SharePoint Server allows an unauthorized attacker to execute code over a network. Microsoft is aware that an exploit for CVE-2025-53770 exists in the wild. Microsoft is preparing and fully testing a comprehensive update t

01What CISA says about this vulnerability

Deserialization of untrusted data in on-premises Microsoft SharePoint Server allows an unauthorized attacker to execute code over a network. Microsoft is aware that an exploit for CVE-2025-53770 exists in the wild. Microsoft is preparing and fully testing a comprehensive update to address this vulnerability. In the meantime, please make sure that the mitigation provided in this CVE documentation…

02Required action — verbatim from CISA

Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

03Notes & references

• msrc.microsoft.com — https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-53770
• arstechnica.com — https://arstechnica.com/security/2025/07/sharepoint-vulnerability-with-9-8-sever…
• github.com — https://github.com/kaizensecurity/CVE-2025-53770
• msrc.microsoft.com — https://msrc.microsoft.com/blog/2025/07/customer-guidance-for-sharepoint-vulnera…
• news.ycombinator.com — https://news.ycombinator.com/item?id=44629710
• research.eye.security — https://research.eye.security/sharepoint-under-siege/
• therecord.media — https://therecord.media/microsoft-sharepoint-zero-day-vulnerability-exploited-gl…
• www.bleepingcomputer.com — https://www.bleepingcomputer.com/news/microsoft/microsoft-sharepoint-zero-day-ex…
• www.cisa.gov — https://www.cisa.gov/news-events/alerts/2025/07/20/microsoft-releases-guidance-e…
• www.darkreading.com — https://www.darkreading.com/remote-workforce/microsoft-rushes-emergency-fix-expl…

04SARA's analyst layer — why this matters

This vulnerability is currently on the CISA KEV list, which CISA only adds CVEs to when there is reliable evidence of active exploitation in the wild. For federal civilian agencies, BOD 22-01 requires remediation by the due date above. For everyone else, KEV is the strongest "patch immediately" signal you can get from public threat intel.

05Affected products (summary)

No structured affected-product list available — see references below for vendor advisories.

06Detection

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection:

Open in Sigma generator →