Security Resilience

CVE-2026-85900

RCE in Microsoft Sharepoint Server ≤ 16.0.20326.20190

RCEDeserialization
Published
13 October 2026
Modified
14 October 2026
Patch / advisory
View advisory
CVSS Score v3.1 8.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.015 74th percentile
Risk Priority 67 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-85900 is a high-severity Deserialization of Untrusted Data (CWE-502) vulnerability in Microsoft Sharepoint Server. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Junk Data (T1001.001); ranked in the top 26% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A08:2025 Software or Data Integrity Failures

EU & UK References

Vulnerability Data

Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.

CWE(s)
CWE-502

Related Threats

MITRE ATT&CK Enterprise Techniques

T1001.001 Junk Data Command And Control
Adversaries may add junk data to protocols used for command and control to make detection more difficult.
attack.mitre.org →
T1001.003 Protocol or Service Impersonation Command And Control
Adversaries may impersonate legitimate protocols or web service traffic to disguise command and control activity and thwart analysis efforts.
attack.mitre.org →
T1003.001 LSASS Memory Credential Access
Adversaries may attempt to access credential material stored in the process memory of the Local Security Authority Subsystem Service (LSASS).
attack.mitre.org →
T1003.007 Proc Filesystem Credential Access
Adversaries may gather credentials from the proc filesystem or `/proc`.
attack.mitre.org →
T1005 Data from Local System Collection
Adversaries may search local system sources, such as file systems, configuration files, local databases, virtual machine files, or process memory, to find files of interest and sensitive data prior to Exfiltration.
attack.mitre.org →
T1006 Direct Volume Access Stealth
Adversaries may directly access a volume to bypass file access controls and file system monitoring.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-54897Same product: Microsoft Sharepoint Server
CVE-2025-59237Same product: Microsoft Sharepoint Server
CVE-2026-105013Same product: Microsoft Sharepoint Server
CVE-2026-66808Same product: Microsoft Sharepoint Server
CVE-2026-66805Same product: Microsoft Sharepoint Server
CVE-2026-65665Same product: Microsoft Sharepoint Server
CVE-2025-49712Same product: Microsoft Sharepoint Server
CVE-2026-45484Same product: Microsoft Sharepoint Server
CVE-2023-33160Same product: Microsoft Sharepoint Server
CVE-2026-64901Same product: Microsoft Sharepoint Server

Affected Assets

microsoft
sharepoint server
≤ 16.0.20326.20190

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation partial match

Developer testing and evaluation can uncover deserialization flaws before deployment.

SA-8 Security and Privacy Engineering Principles partial match

Engineering principles such as safe deserialization and input sanitization structurally prevent the weakness from being introduced.

SI-10 Information Input Validation partial match

Input validation directly stops deserialization of untrusted data by ensuring inputs are valid before processing.

SI-7 Software, Firmware, and Information Integrity partial match

Integrity verification tools can detect malformed or tampered serialized data after the fact.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-02 none match
blocks

PR.PS-02 addresses only post-deployment updates/patching and cannot prevent introduction of unsafe deserialization code, yet it can remediate some instances when the flaw exists in outdated libraries or components.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.14 Information transfer partial match
removes
A.5.15 Access control partial match
removes
A.5.16 Identity management partial match
removes
A.5.17 Authentication information partial match
removes
A.5.18 Access rights partial match
removes
A.8.10 Information deletion partial match
removes

References