CVE-2025-53770 — Deserialization of untrusted data in on-premises Microsoft SharePoint Server all

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 is 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…

02Affected products

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

03Active exploitation status

Yes — actively exploited. Added to the CISA KEV catalog on 2025-07-20. Ransomware use: Known.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection in your stack of choice:

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07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2025-07-20T01:15:30.777
• Last modified: 2026-08-04T05:16:34.887
• Added to CISA KEV: 2025-07-20

09References

• 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…