What is the CVSS score of CVE-2026-65815?

CVE-2026-65815 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: 0.9%.

Which versions of Microsoft Dynamics 365 are affected by CVE-2026-65815?

Microsoft Dynamics 365 on-premises installations are vulnerable to remote code execution (CVE-2026-65815) that allows any authenticated user to fully compromise the server and access all business…. A patch is available.

How to fix or mitigate CVE-2026-65815?

Within 24 hours, inventory all on-premises Dynamics 365 instances, identify those processing critical business data or supporting essential operations, and assess the population of authenticated users with access. Within 7 days, implement compensating controls including network segmentation to isolate Dynamics 365 servers from untrusted networks, enforce multi-factor authentication (MFA) for all user access to these instances, deploy network-based intrusion detection for deserialization payloads, and enable comprehensive audit logging of authentication and serialization activities. Within 30 days, establish regular contact with Microsoft Security Response Center regarding patch timelines, evaluate the feasibility of migrating to Dynamics 365 cloud-hosted solutions, conduct application-level code reviews to identify potential gadget chain exposures, and develop an incident response plan specific to deserialization-based attacks.

Microsoft Dynamics 365 CVE-2026-65815

EUVD-2026-56449 HIGH

Deserialization of Untrusted Data (CWE-502)

2026-08-11 secure@microsoft.com

GHSA-83pg-fr4f-gxq5

Deserialization Microsoft Dynamics 365

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 endpoint (AV:N), no special conditions (AC:L), low-privilege credential required (PR:L); full C/I/A impact is consistent with arbitrary code execution via deserialization gadget chain.

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 - 18:15 vuln.today

CVE Published

Aug 11, 2026 - 17:19 nvd

HIGH 8.8

DescriptionCVE.org

Deserialization of untrusted data in Microsoft Dynamics 365 (on-premises) allows an authorized attacker to execute code over a network.

AnalysisAI

Remote code execution in Microsoft Dynamics 365 on-premises is achievable by any authenticated low-privileged user via a crafted deserialization payload sent over the network, yielding full confidentiality, integrity, and availability compromise of the affected host. The root cause is CWE-502 (Deserialization of Untrusted Data), a class of vulnerability historically weaponized effectively in .NET-based enterprise applications through gadget chains. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access

Obtain valid low-privilege Dynamics 365 credential

Delivery

Send crafted HTTP request with malicious serialized payload

Exploit

Server deserializes untrusted object graph without type restriction

Execution

Gadget chain triggers arbitrary code execution

Persist

Execute commands as application service account

Impact

Exfiltrate CRM data or pivot to host

Access

Obtain valid low-privilege Dynamics 365 credential

Delivery

Send crafted HTTP request with malicious serialized payload

Exploit

Server deserializes untrusted object graph without type restriction

Execution

Gadget chain triggers arbitrary code execution

Persist

Execute commands as application service account

Impact

Exfiltrate CRM data or pivot to host

Vulnerability AssessmentAI

Exploitation	Exploitation requires a valid low-privileged authenticated account within the Microsoft Dynamics 365 on-premises environment - anonymous or unauthenticated network access is insufficient per the CVSS PR:L metric. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment	The CVSS 3.1 score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) signals a high-severity, low-barrier, network-exploitable RCE. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario	An attacker holding any valid Dynamics 365 on-premises user credential - obtained via phishing, credential stuffing, or insider access - sends a specially crafted HTTP request containing a malicious serialized .NET object to a vulnerable deserialization endpoint on the application server. The server processes the payload without adequate type restriction, triggering a gadget chain that executes attacker-controlled code under the application's service account context. …
Remediation	Consult the Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-65815 and apply the update issued for the affected Dynamics 365 on-premises version. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, inventory all on-premises Dynamics 365 instances, identify those processing critical business data or supporting essential operations, and assess the population of authenticated users with access. …

Threat intelligence, references, and detailed analysis are available after sign-in.