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.
Microsoft · SharePoint
Known ransomware use: Known
Follow the source advisory and validate exposure in your environment.
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.
Recent reporting that mentions CVE-2025-53770.
Hackers believed to be associated with China have leveraged the ToolShell vulnerability (CVE-2025-53770) in Microsoft SharePoint in attacks targeting government agencies, universities, telecommunication service providers, and finance organizations. [...]
CVE-2025-53770 and CVE-2025-53771 are vulnerabilities in on-premise Microsoft SharePoint Servers that evolved from previously patched flaws, allowing unauthenticated remote code execution through advanced deserialization and ViewState abuse.
Malicious actors already have already pounced on the zero-day vulnerability, tracked as CVE-2025-53770, to compromise US government agencies and other businesses in ongoing and widespread attacks.
Microsoft has released emergency SharePoint security updates for two zero-day vulnerabilities tracked as CVE-2025-53770 and CVE-2025-53771 that have compromised services worldwide in "ToolShell" attacks. [...]
A critical zero-day vulnerability in Microsoft SharePoint, tracked as CVE-2025-53770, has been actively exploited since at least July 18th, with no patch available and at least 85 servers already compromised worldwide. [...]