Historical catalog analysis: CISA added this entry on July 20, 2025. The entry reflects catalog information retrieved on August 31, 2026, not a snapshot archived on the inclusion date. Check current vendor guidance before acting.
What the vulnerability is
CVE-2025-53770 is a deserialization of untrusted data vulnerability (CWE-502) affecting on-premises installations of Microsoft SharePoint Server. This flaw allows an unauthorized attacker to execute code over a network. The vulnerability is significant because it serves as a patch bypass for CVE-2025-49704 and can be chained with CVE-2025-53771 to facilitate an attack. According to CISA, this vulnerability has been identified for use in known ransomware campaigns.
Exposure and applicability
This vulnerability specifically impacts on-premises SharePoint Server environments. Healthcare providers, health plans, and business associates that utilize local SharePoint servers for administrative documentation, clinical workflows, or the storage of electronic Protected Health Information (ePHI) are at risk.
Organizations using cloud-based SharePoint Online are not listed as affected by this specific vulnerability. However, those maintaining legacy infrastructure—specifically SharePoint Server 2013 and earlier versions—are particularly exposed as these versions have reached end-of-life (EOL) or end-of-service (EOS).
Remediation priorities
Based on the reported risk of ransomware exploitation, we analyze the following priority actions for healthcare security leaders:
- Decommission or Isolate EOL Systems: Public-facing instances of SharePoint Server 2013 and earlier should be disconnected immediately. These versions no longer receive security updates, making them permanent targets for known exploits.
- Apply Updated Patches: For supported versions, administrators should apply the latest vendor updates. Because CVE-2025-53770 bypasses previous fixes (CVE-2025-49704), relying on older patches is insufficient; the most recent robust protections must be implemented.
- Network Segmentation: To limit potential damage, SharePoint servers should not be directly exposed to the public internet unless absolutely necessary and protected by stringent access controls. This reduces the likelihood of initial network-based execution by unauthorized actors.
How to validate remediation
To verify that exposure has been reduced, security teams should perform the following checks:
- Version Audit: Confirm through system inventories that no public-facing SharePoint Server 2013 or earlier versions remain active. This is a baseline check for EOL status.
- Patch Verification: Cross-reference installed update IDs against the vendor’s specific guidance for CVE-2025-53770 to ensure the patch bypass has been addressed.
- Connectivity Review: Validate that on-premises SharePoint servers are not reachable via public IP addresses without passing through authorized security gateways (e.g., VPN or Zero Trust Network Access).
Limits and open questions
Applying these updates could reduce the likelihood of exploitation, but it does not guarantee immunity from all ransomware vectors. A primary limitation is the existence of legacy EOL systems; if an organization cannot disconnect these servers due to clinical dependencies, they remain fundamentally vulnerable as no official patch exists for those versions.
Additionally, while this analysis addresses the network-based execution path, it remains unknown how many healthcare environments have already been targeted via the chaining of CVE-2025-53771. Organizations should coordinate with their clinical engineering and IT teams to ensure that patching schedules do not disrupt critical patient care systems.
Source and editorial note
CVE-2025-53770: Microsoft SharePoint Deserialization of Untrusted Data Vulnerability · Source date: July 20, 2025 · Retrieved August 31, 2026.
Material facts are tied to the cited primary source. Recommendations are independent defensive analysis unless attributed to the source. Confirm consequential decisions against current authoritative guidance.
Archive date: July 23, 2025. The displayed post date is assigned three days after the source date to organize this retrospective archive; it does not mean this site published the analysis then. First published by this site: October 05, 2026 at 01:09 UTC.
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