CVE Alert: CVE-2025-53770 – Microsoft – Microsoft SharePoint Enterprise Server 2016
CVE-2025-53770
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.
AI Summary Analysis
Risk verdict
Critical remote code execution on on‑prem SharePoint Server with active exploitation; treat as priority 1.
Why this matters
An attacker can run arbitrary code without user interaction, potentially taking full control of the SharePoint server and escalating to adjacent systems or sensitive data. In practice, this enables rapid lateral movement, data exposure, and disruption across organisations relying on SharePoint for collaboration and document management.
Most likely attack path
- Attack vector: network-based, no user interaction required.
- Preconditions: exploit exists in the wild; affected on-prem instances exposed to the internet or poorly segmented networks.
- Potential impact: attacker achieves high-privilege code execution with no credentials, enabling immediate data access, persistence, and lateral movement.
Who is most exposed
Organisations running unpatched SharePoint Server 2016/2019 or Subscription Edition, especially those with internet-facing endpoints or flat internal trusts without segmenting and monitoring.
Detection ideas
- Sudden process start patterns or memory tampering on SharePoint/web app services.
- Deserialization error traces or anomalous deserialization activity in application logs.
- Unusual, high-volume network activity to/from known SharePoint hosts with no legitimate admin actions.
- Unexpected system or service account activity, including privilege escalation steps.
- EDR or network sensors flagging untrusted payloads or rapid asset discovery post-initial access.
Mitigation and prioritisation
- Patch immediately when available; treat as priority 1 due to KEV and exploitation in the wild.
- Apply vendor mitigations per MSRC guidance if patching is not yet possible; review workaround steps.
- Implement network segmentation, restrict internet exposure of SharePoint servers, and harden authentication/least privilege.
- Enhance monitoring for deserialization anomalies and unusual process flows; deploy targeted detections and alerting.
- Expedite change-management and testing windows to reduce dwell time on affected systems.
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