CVE-2026-40368
Published: 12 May 2026
Summary
CVE-2026-40368 is a high-severity Deserialization of Untrusted Data (CWE-502) vulnerability in Microsoft Sharepoint Server. Its CVSS base score is 8.0 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 21.4% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
Deeper analysis
The vulnerability CVE-2026-40368 stems from deserialization of untrusted data, tracked as CWE-502, in Microsoft Office SharePoint. It received a CVSS 3.1 base score of 8.0 reflecting network attack vector, low complexity, limited privileges, and required user interaction that nonetheless yields high impact on confidentiality, integrity, and availability.
An authorized attacker with network access can supply malicious serialized data to trigger remote code execution on the affected SharePoint instance, achieving full control over the target system.
The official advisory published by Microsoft at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40368 addresses remediation steps and patch availability. The associated EPSS score remains low and unchanged at a peak of 0.0112 with no observed increase after disclosure.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-29650
Vulnerability details
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Deserialization RCE in public-facing SharePoint server directly enables remote exploitation of the application.
CVEs Like This One
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Penetration testing supplies malicious serialized objects, detecting unsafe deserialization and supporting corrective actions.
Evaluation of untrusted data handling (deserialization testing) reveals unsafe processing, which the required remediation process addresses.
Untrusted serialized data can be deserialized and observed inside the chamber, blocking gadget-chain exploitation outside the sandbox.
Validates or rejects untrusted serialized data before deserialization occurs.
Identifies and blocks malicious code introduced through deserialization of untrusted data at system boundaries.
Integrity verification of serialized information can detect tampering before deserialization occurs.
Provenance of associated data allows detection of untrusted sources before deserialization or processing occurs.