Security readout for executives and security teams
Plain-English summary
CVE-2026-26108 is a Microsoft Excel remote code execution flaw caused by a heap-based buffer overflow. The CVSS data says exploitation requires user interaction and local execution context, but successful exploitation could compromise confidentiality, integrity, and availability on the affected system.
Executive priority
Prioritize this in the normal high-severity patch cycle, especially for teams handling external spreadsheets. No active exploitation is cited, but impact is full system compromise if successfully triggered.
Technical view
The source bundle identifies CWE-122 in Microsoft Office Excel with CVSS 3.1 score 7.8, AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Affected products include Microsoft 365 Apps for Enterprise, Excel 2016, Office 2019, Office LTSC 2021/2024, Mac LTSC editions, and Office Online Server.
Likely exposure
Organizations running the listed Microsoft Excel, Office, Microsoft 365 Apps for Enterprise, Mac LTSC, or Office Online Server versions may be exposed until vendor updates are applied.
Exploitation context
The bundle does not show CISA KEV listing or active exploitation. CVSS marks exploit code maturity as unproven and requires user interaction, so treat exploitation as plausible but not source-confirmed as active.
Researcher notes
Evidence is limited to the provided CVE and MSRC metadata. The bundle confirms heap-based overflow, affected product families, CVSS vector, and patch availability, but does not provide root-cause details, indicators, exploit method, or detection logic.
Mitigation direction
- Apply the Microsoft security update for CVE-2026-26108 to affected Office and Excel installations.
- Include Office Online Server in patch scope if deployed.
- Prioritize systems that regularly handle external spreadsheets.
- Check Microsoft MSRC guidance for product-specific update details.
- Monitor Microsoft advisories for later corrections or superseding updates.
Validation and detection
- Inventory Office, Excel, Microsoft 365 Apps, and Office Online Server versions.
- Compare installed versions against the affected products in the source bundle.
- Verify the relevant Microsoft update is installed on Windows and Mac endpoints.
- Confirm Office Online Server patch status separately from desktop Office.
- Document exceptions where unsupported or unpatched versions remain.
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-122: 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-2026-26108 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.
Heap-based Buffer Overflow
Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.