Security readout for executives and security teams
Plain-English summary
An authenticated attacker with network access could exploit unsafe data handling in affected Microsoft SharePoint Server deployments to run code. Successful exploitation could expose information, alter content, disrupt service, or enable broader compromise. The vulnerability is rated high severity at CVSS 8.8.
Executive priority
Treat this as a high-priority remediation because a low-privileged authenticated attacker could gain code execution without user interaction. Accelerate patching for internet-facing, partner-accessible, or widely used deployments. The sources do not support declaring an active exploitation emergency.
Technical view
CVE-2026-40365 is a CWE-1220 deserialization vulnerability affecting listed SharePoint Server 2016, 2019, and Subscription Edition versions. Exploitation requires low privileges, network access, low complexity, and no user interaction. Successful exploitation affects confidentiality, integrity, and availability within the vulnerable system's security scope.
Likely exposure
Exposure is highest where affected SharePoint servers are network-reachable by untrusted or compromised authenticated accounts. The supplied records identify version 16.0.0 for each listed product, but provide no configuration-specific exposure criteria. Organizations should confirm applicability using Microsoft's advisory and their deployed build information.
Exploitation context
The supplied bundle does not report CISA KEV inclusion or provide evidence of active exploitation. It indicates that an authorized attacker can exploit the flaw remotely without user interaction. No public exploit availability or observed attack activity is established by these sources.
Researcher notes
The CVSS 3.1 vector is AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, with exploit maturity unproven and an official remedy available. The bundle does not document vulnerable components, attack prerequisites beyond authorization, affected build ranges beyond 16.0.0, indicators, or exploitation telemetry. Consult Microsoft for implementation-level remediation details.
Mitigation direction
- Inventory SharePoint Server 2016, 2019, and Subscription Edition deployments and record their exact builds.
- Review Microsoft's CVE advisory and apply the applicable vendor security update according to change procedures.
- Prioritize externally reachable or broadly accessible SharePoint servers for remediation.
- Restrict SharePoint network access and authenticated access to necessary users while remediation is pending.
- Monitor Microsoft guidance for revised affected-version, mitigation, or update information.
Validation and detection
- Confirm every SharePoint server's edition, version, build, and update status.
- Compare installed builds against Microsoft's CVE advisory and applicable update guidance.
- Verify the security update installed successfully and services returned to normal operation.
- Reassess network reachability and remove unnecessary external or internal access paths.
- Review authentication and server telemetry for suspicious activity; supplied sources provide no specific indicators.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-1220: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-40365 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C2.85.9microsoftVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- Microsoft SharePoint Server Remote Code Execution VulnerabilityCVE reference, microsoft · vendor-advisory, patch
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Insufficient Granularity of Access Control
Insufficient Granularity of Access Control represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.