Microsoft SharePoint Server Deserialization Vulnerability (CVE‑2026‑45659) Enables Remote Code Execution
What It Is – Microsoft SharePoint Server suffers a deserialization of untrusted data flaw that lets an attacker who can submit crafted objects cause arbitrary code execution on the server. The issue is tracked as CVE‑2026‑45659 and has been assigned a CVSS v3.1 base score of 8.8 (High).
Exploitability – The vulnerability is exploitable over the network by an authenticated attacker; proof‑of‑concept code is publicly available, and Microsoft has issued a security advisory with a patch.
Affected Products – Microsoft SharePoint Server (on‑premises) versions prior to the September 2026 security update.
Why It Matters for Trust & Control Assurance
- Demonstrates the need for secure coding and input‑validation controls that map to multiple frameworks (e.g., NIST CSF 2.0 Protect‑PR.DS‑1).
- Patch management and evidence of timely remediation are key audit artifacts for any control‑assurance program.
- Continuous monitoring of vulnerability status feeds defensible evidence that the organization maintains a trusted security posture.
Recommended Actions
- Apply Microsoft’s September 2026 security update for SharePoint Server immediately.
- Verify remediation with an authenticated scan or penetration test that attempts the deserialization exploit.
- Update your control‑mapping repository to record the patch as evidence of “secure development / input validation” compliance.
- Incorporate the vulnerability into your continuous monitoring feed to ensure future regressions are detected.
Source: CISA KEV – CVE‑2026‑45659