Security readout for executives and security teams
Plain-English summary
CVE-2025-21366 is a high-severity Microsoft Access remote code execution flaw. Successful exploitation could let code run with serious confidentiality, integrity, and availability impact, but the CVSS data says user interaction is required and exploit maturity is unproven.
Executive priority
Treat as a high-priority patching item for Office-heavy environments. It requires user interaction, but successful exploitation could produce full impact to data and system availability on affected endpoints.
Technical view
The source bundle identifies a CWE-416 use-after-free issue in Microsoft Access/Office products with CVSS 3.1 score 7.8. Vector is local, low complexity, no privileges required, user interaction required, unchanged scope, and high C/I/A impact. Microsoft lists remediation in its advisory.
Likely exposure
Exposure is most likely where Microsoft Access 2016, Office 2019, Office LTSC 2021/2024, or Microsoft 365 Apps for Enterprise are installed and users handle Access or Office content.
Exploitation context
The CVE is not marked as KEV in the provided bundle. The CVSS exploit maturity is unproven. The evidence supports user-assisted local exploitation, but does not provide confirmed active exploitation or delivery details.
Researcher notes
The provided evidence is limited to Microsoft and CVE metadata. Key known facts are CWE-416, affected product families, CVSS 7.8, UI:R, AV:L, and MSRC patch availability. No public exploit confirmation is provided.
Mitigation direction
- Apply the Microsoft security update referenced by MSRC.
- Inventory affected Microsoft Access and Office installations.
- Prioritize systems where users open external Office or Access files.
- Follow Microsoft advisory guidance for any product-specific actions.
- Monitor Microsoft guidance for revisions or supersedence.
Validation and detection
- Confirm installed Office and Access versions across endpoints.
- Verify the relevant Microsoft update is installed.
- Compare assets against the affected product list.
- Check vulnerability management tools for CVE-2025-21366 detection.
- Review endpoint telemetry for unusual Access or Office child processes.
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-416: 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-2025-21366 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
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C1.85.9microsoftVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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 Access 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.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.