Security readout for executives and security teams
Plain-English summary
This flaw can cause affected Windows systems to lose availability through the TCP/IP component. It does not indicate data theft or modification. The supplied CVSS score is 7.1 (high), and the local attack vector limits direct internet exposure, but disruption of important workstations or servers could still affect operations.
Executive priority
Treat as a high-priority availability issue, not an emergency remote-compromise event. Patch critical and locally exposed systems promptly, then complete fleet-wide remediation through the standard security-update cycle. Escalate systems that cannot be updated or whose downtime would materially affect business services.
Technical view
CVE-2026-40401 is a Windows TCP/IP denial-of-service vulnerability associated with CWE-476, indicating a null-pointer dereference. The supplied vector requires local access but no privileges or user interaction, changes scope, and affects availability only. Microsoft’s advisory is identified as providing an official patch.
Likely exposure
Exposure applies to the listed Windows 10 and 11 releases and Windows Server 2012 through 2025 variants when the applicable Microsoft security update is absent. Prioritize operationally critical servers, shared systems, and endpoints where untrusted local users or processes may operate. The bundle does not establish network-remote exploitation.
Exploitation context
The supplied record is not in CISA KEV, and its CVSS exploit-maturity metric is unproven. No cited source in the bundle establishes active exploitation or public exploit availability. Because the vector is local, an attacker would first need an execution path or other local access to an affected system.
Researcher notes
The evidence supports denial of service through a CWE-476 condition, but does not describe the triggering path, crash behavior, prerequisites beyond the CVSS vector, or indicators of compromise. Do not infer remote reachability from the TCP/IP component name; the supplied score explicitly specifies AV:L. Consult Microsoft for exact build and update applicability.
Mitigation direction
- Review Microsoft’s CVE advisory and identify the applicable security update for each affected Windows release.
- Deploy the Microsoft update using normal change-control and expedited procedures for critical systems.
- Prioritize systems allowing untrusted local access or running workloads with elevated availability requirements.
- Use Microsoft-supported guidance for any temporary mitigation if immediate patching is not possible.
Validation and detection
- Inventory Windows editions, versions, and builds against Microsoft’s affected-product table.
- Confirm the applicable Microsoft security update is installed and successfully reported by endpoint management.
- Re-scan patched assets and investigate systems with missing, failed, or pending updates.
- Review availability and crash records for unexplained TCP/IP-related disruption; no specific indicators were supplied.
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-476: 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 lookupCVE-2026-40401 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
- 7.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/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:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C2.54microsoftVulnerability scoring details
Base CVSS 3.1 score
7.1HighVector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/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
- Windows TCP/IP Denial of Service 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.
NULL Pointer Dereference
NULL Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.