CVE-2026-64901Network attack vector

Authenticated code execution via unsafe deserialization

Published Aug 11, 2026 · Updated Aug 25, 2026

Deserialization of untrusted data in Microsoft SharePoint Server 2016, 2019, and Subscription Edition allows remote authenticated users to execute code. Microsoft has disclosed only the weakness class; public records do not identify the deserialization entry point, object type, or request path that accepts untrusted serialized data. Successful exploitation requires valid SharePoint credentials and network reachability to the server, and the published scoring indicates full confidentiality, integrity, and availability impact once code runs.

CVSS severityUnavailable
Unscored
EPSS probability1.91%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

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Summary

What happened

Deserialization of untrusted data in Microsoft SharePoint Server 2016, 2019, and Subscription Edition allows remote authenticated users to execute code. Microsoft has disclosed only the weakness class; public records do not identify the deserialization entry point, object type, or request path that accepts untrusted serialized data. Successful exploitation requires valid SharePoint credentials and network reachability to the server, and the published scoring indicates full confidentiality, integrity, and availability impact once code runs.

The record

CVE
CVE-2026-64901
Published
Aug 11, 2026
Updated
Aug 25, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-502, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.8MicrosoftCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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