Security readout for executives and security teams
Plain-English summary
CVE-2026-26107 is a high-severity Microsoft Excel vulnerability that could let an unauthorized attacker run code on a local system. The CVSS data says user interaction is required, so business risk centers on users and services processing Office content from untrusted sources.
Executive priority
Treat as a high-priority patching item, especially for users who receive external spreadsheets or operate shared Office processing services. No active exploitation is evidenced in the provided sources, but the impact is full code execution with high CIA impact.
Technical view
The issue is a use-after-free flaw in Microsoft Office Excel, mapped to CWE-416. It has CVSS 3.1 score 7.8 with local attack vector, low complexity, no privileges required, required user interaction, and high confidentiality, integrity, and availability impact.
Likely exposure
Potentially exposed assets include affected Microsoft 365 Apps for Enterprise, Excel 2016, Office 2019, Office LTSC 2021/2024, Office LTSC for Mac 2021/2024, and Office Online Server versions listed in the source bundle.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. CVSS marks exploit maturity as unproven. The local attack vector and required user interaction mean exposure depends on vulnerable installations and user or server-side handling of Office content.
Researcher notes
Evidence is limited to the CVE source bundle and Microsoft advisory reference. The bundle names the weakness class, affected products, CVSS vector, and patch reference, but does not provide root-cause detail, exploit artifacts, indicators, or workaround specifics.
Mitigation direction
- Apply Microsoft updates from the CVE-2026-26107 vendor advisory.
- Prioritize endpoints and servers that process external Office documents.
- Reduce exposure to untrusted Office files until patched.
- Check Microsoft guidance for any product-specific workarounds or deployment notes.
Validation and detection
- Inventory affected Microsoft Office and Excel versions across endpoints and servers.
- Confirm installed Office builds include the Microsoft fix for CVE-2026-26107.
- Review Office Online Server patch status where deployed.
- Check email, web, and file-sharing controls for untrusted Office document handling.
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-2026-26107 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.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.