ToolShell (CVE-2025-53770)
Microsoft SharePoint Server Remote Code Execution Vulnerability
Microsoft SharePoint Deserialization of Untrusted Data Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.
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.
CISA notes
CISA Mitigation Instructions: 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
Also Known as ToolShell
Part of the ToolShell set of on-premises SharePoint Server flaws exploited from mid-July 2025. The name first described the CVE-2025-49706 and CVE-2025-49704 chain; Microsoft and Unit 42 also apply it to CVE-2025-53770, a deserialization variant enabling unauthenticated code execution.
Name sources
- UPDATE: Microsoft Releases Guidance on Exploitation of SharePoint Vulnerabilities (CISA)
- Disrupting active exploitation of on-premises SharePoint vulnerabilities (Microsoft Security Blog)
- Active Exploitation of Microsoft SharePoint Vulnerabilities (Unit 42)
- SharePoint Under Siege: ToolShell Exploit (Eye Security)
Description
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 is in place so that you are protected from exploitation.
Severity
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:W/RC:CAffected Products
| Vendor | Product | Affected versions |
|---|---|---|
| Microsoft | Microsoft SharePoint Enterprise Server 2016 | 16.0.0 to <16.0.5513.1001 |
| Microsoft | Microsoft SharePoint Server 2019 | 16.0.0 to <16.0.10417.20037 |
| Microsoft | Microsoft SharePoint Server Subscription Edition | 16.0.0 to <16.0.18526.20508 |
References
12 Links- https://msrc.microsoft.com/blog/2025/07/customer-guidance-for-sharepoint-vulnerability-cve-2025-53770/
- https://www.cisa.gov/news-events/alerts/2025/07/20/microsoft-releases-guidance-exploitation-sharepoint-vulnerability-cve-2025-53770
- https://research.eye.security/sharepoint-under-siege/
- https://www.bleepingcomputer.com/news/microsoft/microsoft-sharepoint-zero-day-exploited-in-rce-attacks-no-patch-available/
- https://www.forbes.com/sites/daveywinder/2025/07/20/microsoft-confirms-ongoing-mass-sharepoint-attack---no-patch-available/
- https://x.com/Shadowserver/status/1946900837306868163
- https://github.com/kaizensecurity/CVE-2025-53770
- https://therecord.media/microsoft-sharepoint-zero-day-vulnerability-exploited-globally
- https://news.ycombinator.com/item?id=44629710
- https://arstechnica.com/security/2025/07/sharepoint-vulnerability-with-9-8-severity-rating-is-under-exploit-across-the-globe/
- https://www.darkreading.com/remote-workforce/microsoft-rushes-emergency-fix-exploited-sharepoint-toolshell-flaw
Record Details
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Microsoft SharePoint Server Spoofing Vulnerability
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Related
Tool categories
CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.