Security readout for executives and security teams
Plain-English summary
This is a critical Microsoft Windows NTLMv1 privilege-escalation vulnerability. The provided sources identify affected Windows 11 24H2 and Windows Server 2022/2025 builds. Microsoft published an advisory with a patch reference. No provided source says it is being actively exploited.
Executive priority
Treat as urgent patching for affected Windows estates because the score is critical and the attack vector is network-based with no user interaction required.
Technical view
CVE-2025-21311 is a CWE-303 issue in Windows NTLMv1 with CVSS 3.1 score 9.8. The vector is network-accessible, low complexity, requires no privileges or user interaction, and rates confidentiality, integrity, and availability impact as high. The bundle does not describe exploit mechanics.
Likely exposure
Exposure is limited by the bundle to listed Microsoft Windows 11 Version 24H2, Windows Server 2022 23H2 Server Core, Windows Server 2025, and Windows Server 2025 Server Core builds.
Exploitation context
The bundle marks CISA KEV status as false and CVSS exploit maturity as unproven. Treat active exploitation as unconfirmed from these sources, not absent in the wild.
Researcher notes
Evidence is sparse. The public bundle provides severity, affected products, CWE-303, CVSS vector, KEV false, and MSRC patch reference, but not root-cause detail or exploitation procedure.
Mitigation direction
- Apply the Microsoft update referenced by the MSRC advisory.
- Prioritize internet-facing, authentication, and server workloads running listed affected builds.
- Check MSRC guidance before changing NTLMv1 configuration or applying compensating controls.
- Track vendor advisory updates for revised affected versions or operational mitigations.
Validation and detection
- Inventory Windows assets for the exact affected products and builds listed.
- Confirm the applicable Microsoft security update is installed on affected systems.
- Review authentication logs for unusual NTLMv1-related activity without assuming exploitation.
- Document exceptions and revisit them when Microsoft updates the advisory.
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-303: 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 lookupPrivilege behavior lookup
The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2025-21311 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
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/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:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C3.95.9microsoftVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/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
- Windows NTLM V1 Elevation of Privilege 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.
Incorrect Implementation of Authentication Algorithm
Incorrect Implementation of Authentication Algorithm represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.