Security readout for executives and security teams
Plain-English summary
A flaw in Microsoft Excel can allow code execution when a user interacts with malicious content. Successful exploitation could compromise data, alter systems, or disrupt operations with the user’s permissions. Microsoft rates the issue high severity, with a CVSS score of 7.8.
Executive priority
Treat remediation as a high-priority endpoint update. The potential impact is full compromise of confidentiality, integrity, and availability, although exploitation requires user interaction and active exploitation is not established. Track update coverage and exceptions until affected installations are remediated.
Technical view
CVE-2026-20946 is a CWE-125 out-of-bounds read in Microsoft Office Excel. The CVSS vector indicates local attack access, low complexity, no prior privileges, and required user interaction. Successful exploitation can cause high confidentiality, integrity, and availability impact without changing security scope.
Likely exposure
Exposure applies to the listed Microsoft 365 Apps for Enterprise, Excel 2016, Office 2019, and Office LTSC 2021 or 2024 products, including listed Mac editions. Actual exposure depends on installed versions and whether Microsoft’s applicable security update is present.
Exploitation context
The supplied evidence does not establish active exploitation, and the CVE is not identified as being in KEV. CVSS records exploit maturity as unproven. User interaction is required, but the sources do not describe the delivery method, trigger format, or attack prerequisites beyond the published vector.
Researcher notes
The public bundle identifies an out-of-bounds read but provides no root-cause detail, vulnerable component, triggering structure, fixed build, or proof of concept. Researchers should rely on Microsoft’s advisory for exact update applicability. Absence from KEV should not be interpreted as proof that exploitation has never occurred.
Mitigation direction
- Inventory installations of every listed Microsoft Office and Excel product.
- Review Microsoft’s advisory for applicable security updates and deployment requirements.
- Apply the Microsoft-provided update to affected installations using normal change controls.
- Prioritize systems whose users regularly handle externally supplied Excel content.
Validation and detection
- Compare installed product editions and versions against Microsoft’s advisory.
- Confirm the applicable Microsoft security update is installed across managed endpoints.
- Identify deployment failures, deferred devices, and unmanaged installations requiring follow-up.
- Recheck Microsoft guidance for revisions affecting product scope or remediation.
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-125: 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-2026-20946 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 Excel 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.
Out-of-bounds Read
Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.