Critical Deserialization Vulnerability in Microsoft SharePoint Server (CVE‑2025‑53770) Enables Remote Code Execution
What It Is – Microsoft SharePoint Server on‑premises contains a deserialization‑of‑untrusted‑data flaw that can allow an unauthenticated attacker to execute arbitrary code over the network. The issue can be chained with CVE‑2025‑53771 and bypasses earlier mitigations for CVE‑2025‑49704.
Exploitability – Publicly disclosed; proof‑of‑concept code is available and Microsoft has issued a security update that adds stronger protection. CVSS v3.1 score is rated High (≈7.8).
Affected Products – Microsoft SharePoint Server (all supported on‑premises versions prior to the latest security update).
Why It Matters for Trust & Control Assurance
- Demonstrates the need for continuous vulnerability‑management evidence; auditors expect proof that known flaws are tracked and remediated promptly.
- Highlights gaps in secure‑development and code‑review controls; a robust control‑mapping program can surface such weaknesses before they reach production.
- Provides a concrete test of the VCF control objective Application Security & Vulnerability Management, which maps to many frameworks (e.g., NIST CSF 2.0, ISO 27001).
Recommended Actions
- Apply Microsoft’s latest SharePoint security update immediately.
- Verify that the patch is deployed across all on‑premises SharePoint instances via automated inventory.
- Update your vulnerability‑management register to reflect CVE‑2025‑53770, capture remediation evidence, and map the finding to the “Application Security” control area in your framework of record.
- Conduct a targeted code‑review of any custom SharePoint solutions that deserialize external data.
- Test for the presence of CVE‑2025‑53771 chaining to ensure full remediation.
Source: CISA KEV – CVE‑2025‑53770