What is the CVSS score of EUVD-2026-56573?

EUVD-2026-56573 has a CVSS 3.1 base score of 8.8 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 1.3%.

Which versions of Microsoft SharePoint are affected by EUVD-2026-56573?

Microsoft Office SharePoint contains a remote code execution vulnerability (CVSS 8.8) enabling authenticated users with low-level access to execute arbitrary code and compromise system…. A patch is available.

How to fix or mitigate EUVD-2026-56573?

Within 24 hours: inventory all SharePoint deployments, identify business-critical instances, and document current user access privileges. Within 7 days: restrict SharePoint access to users with documented business need, enforce network segmentation to limit lateral movement from compromised accounts, and enable detailed audit logging on deserialization events and administrative actions. Within 30 days: establish a vendor patch monitoring process with Microsoft and apply security updates immediately upon release; evaluate architectural alternatives or temporary air-gapping for highest-risk instances if extended patch delay occurs.

Microsoft SharePoint EUVD-2026-56573

| CVE-2026-70321 HIGH

Deserialization of Untrusted Data (CWE-502)

2026-08-11 secure@microsoft.com

GHSA-h6gw-pxjf-hvrf

Deserialization Microsoft Sharepoint Server

8.8

CVSS 3.1 · Vendor: microsoft

Severity by source

Vendor (microsoft) PRIMARY

8.8 HIGH

AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

vuln.today AI

8.8 HIGH

Network-reachable deserialization endpoint requires low-privilege authentication; full code execution yields high C/I/A with no scope change.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (microsoft).

CVSS VectorVendor: microsoft

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Patch available

Aug 11, 2026 - 18:19 EUVD

Analysis Generated

Aug 11, 2026 - 17:53 vuln.today

CVE Published

Aug 11, 2026 - 17:19 nvd

HIGH 8.8

DescriptionCVE.org

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

AnalysisAI

Remote code execution in Microsoft Office SharePoint allows an attacker authenticated with low privileges to execute arbitrary code over a network via unsafe deserialization of user-controlled data. The CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) confirms full confidentiality, integrity, and availability impact with no user interaction required. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access

Obtain low-privilege SharePoint credentials

Delivery

Craft malicious serialized .NET object

Exploit

Submit payload to vulnerable SharePoint endpoint

Execution

Trigger unsafe deserialization on server

Impact

Execute arbitrary code as SharePoint service account

Access

Obtain low-privilege SharePoint credentials

Delivery

Craft malicious serialized .NET object

Exploit

Submit payload to vulnerable SharePoint endpoint

Execution

Trigger unsafe deserialization on server

Impact

Execute arbitrary code as SharePoint service account

Vulnerability AssessmentAI

Exploitation	The attacker must hold an authenticated account with low-privilege access to the target SharePoint instance - the CVSS vector PR:L confirms authentication is required. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment	The CVSS base score of 8.8 (High) is consistent with the vector metrics: network-accessible (AV:N), low attack complexity (AC:L), low privilege required (PR:L), no user interaction (UI:N), and full C/I/A impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario	An attacker with a valid low-privilege SharePoint account crafts a malicious serialized object targeting a known .NET gadget chain and submits it to a vulnerable SharePoint endpoint that deserializes user-supplied data without adequate type validation. The SharePoint application server deserializes the payload and executes the embedded arbitrary commands in the context of the SharePoint service account. …
Remediation	Apply the security update issued by Microsoft for this vulnerability, referenced at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70321. … Detailed patch versions, workarounds, and compensating controls in full report.