CVE-2025-53770
Published: 20 July 2025
Summary
CVE-2025-53770 is a critical-severity Deserialization of Untrusted Data (CWE-502) vulnerability in Microsoft Sharepoint Server. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 0.5% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 SC-7 (Boundary Protection) and SI-10 (Information Input Validation).
Deeper analysis
CVE-2025-53770 is a deserialization of untrusted data vulnerability (CWE-502) affecting on-premises Microsoft SharePoint Server. The flaw permits remote code execution over a network and carries a CVSS 3.1 base score of 9.8 reflecting network attack vector, low complexity, and no required privileges or user interaction.
An unauthenticated attacker can send specially crafted serialized data to an exposed SharePoint server and achieve arbitrary code execution, resulting in full confidentiality, integrity, and availability impact on the affected system. Microsoft has confirmed that working exploits for this issue are already present in the wild.
Microsoft is preparing a comprehensive security update but currently directs customers to apply the mitigation steps documented in the CVE advisory until the patch is released. Guidance is available on the Microsoft Security Response Center pages for CVE-2025-53770 and the associated customer blog post.
Public reporting indicates active exploitation across multiple organizations, consistent with the vulnerability’s high EPSS scores (current 0.8818, peak 0.9105).
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-23309
Vulnerability details
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…
more
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.
- CWE(s)
- KEV Date Added
- 20 July 2025
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Direct unauthenticated RCE on public-facing SharePoint Server via deserialization flaw matches T1190 exploitation vector for initial access and full compromise.
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Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Mandates timely identification, reporting, and correction of system flaws, including application of Microsoft-provided mitigations for this actively exploited deserialization vulnerability.
Enforces information flow controls at system boundaries to block unauthorized network access required for remote code execution via deserialization.
Validates untrusted network inputs to prevent processing of malicious serialized data that triggers arbitrary code execution in SharePoint Server.