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NVD / CVE Program· CNA microsoft

CVE-2026-21259: Microsoft Excel Elevation of Privilege Vulnerability

HighCVSS 7.8 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.55% (FIRST EPSS).
  • Someone with local access to the system can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • Fixed version: Microsoft 365 Apps for Enterprise for 32-bit Systems https://aka.ms/OfficeSecurityReleases; Microsoft 365 Apps for Enterprise for 64-bit Systems https://aka.ms/OfficeSecurityReleases; Microsoft Excel 2016 (32-bit edition) 16.0.5539.1002.

Low priority for now. Upgrade to Microsoft 365 Apps for Enterprise for 32-bit Systems https://aka.ms/OfficeSecurityReleases; Microsoft 365 Apps for Enterprise for 64-bit Systems https://aka.ms/OfficeSecurityReleases; Microsoft Excel 2016 (32-bit edition) 16.0.5539.1002 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to elevate privileges locally.

Published
Feb 10, 2026
Updated
Aug 19, 2026
EPSS
0.5% · 46th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · microsoft
7.8
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-21259

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
microsoft365 apps
microsoftexcel
microsoftoffice
microsoftoffice long term servicing channel
microsoftoffice online server

Versions reported by the vendor

Affected version ranges reported by the assigning authority (microsoft). Independent of NVD's CPE analysis and usually ahead of it.

  • Microsoft Microsoft 365 Apps for Enterprise

    • 16.0.1 and later · before https://aka.ms/OfficeSecurityReleasesaffected

  • Microsoft Microsoft Excel 2016

    • 16.0.0.0 and later · before 16.0.5539.1002affected

  • Microsoft Microsoft Office 2019

    • 19.0.0 and later · before https://aka.ms/OfficeSecurityReleasesaffected

  • Microsoft Microsoft Office LTSC 2021

    • 16.0.1 and later · before https://aka.ms/OfficeSecurityReleasesaffected

  • Microsoft Microsoft Office LTSC 2024

    • 16.0.0 and later · before https://aka.ms/OfficeSecurityReleasesaffected

  • Microsoft Office Online Server

    • 16.0.0.0 and later · before 16.0.10417.20097affected
Affected versions · NVD (6)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • microsoft 365 appsall versions
  • microsoft excel2016
  • microsoft office2019
  • microsoft office long term servicing channel2021
  • microsoft office long term servicing channel2024
  • microsoft office online serverbefore 16.0.10417.20097

Same product

microsoft: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-23397Microsoft Outlook Elevation of Privilege VulnerabilityKEV
    98Now
  • CVE-2024-21413Microsoft Outlook Remote Code Execution VulnerabilityKEV
    97Now
  • CVE-2026-21509Microsoft Office Security Feature Bypass VulnerabilityKEV
    82Now

Published before and after this one in the same product

  • ← EarlierCVE-2026-20957Jan 13, 2026 · Microsoft Excel Remote Code Execution Vulnerability
    31Monitor
  • ← EarlierCVE-2026-21258Feb 10, 2026 · Microsoft Excel Information Disclosure Vulnerability
    22Monitor
  • Later →CVE-2026-21260Feb 10, 2026 · Microsoft Outlook Spoofing Vulnerability
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Microsoft 365 Apps for Enterprise for 32-bit Systemshttps://aka.ms/OfficeSecurityReleases · Click to RunMicrosoft (MSRC)
Microsoft 365 Apps for Enterprise for 64-bit Systemshttps://aka.ms/OfficeSecurityReleases · Click to RunMicrosoft (MSRC)
Microsoft Excel 2016 (32-bit edition)16.0.5539.1002 · KB5002837Microsoft (MSRC)
Microsoft Excel 2016 (64-bit edition)16.0.5539.1002 · KB5002837Microsoft (MSRC)
Microsoft Office 2019 for 32-bit editionshttps://aka.ms/OfficeSecurityReleases · Click to RunMicrosoft (MSRC)
Microsoft Office 2019 for 64-bit editionshttps://aka.ms/OfficeSecurityReleases · Click to RunMicrosoft (MSRC)
Microsoft Office LTSC 2021 for 32-bit editionshttps://aka.ms/OfficeSecurityReleases · Click to RunMicrosoft (MSRC)
Microsoft Office LTSC 2021 for 64-bit editionshttps://aka.ms/OfficeSecurityReleases · Click to RunMicrosoft (MSRC)
Microsoft Office LTSC 2024 for 32-bit editionshttps://aka.ms/OfficeSecurityReleases · Click to RunMicrosoft (MSRC)
Microsoft Office LTSC 2024 for 64-bit editionshttps://aka.ms/OfficeSecurityReleases · Click to RunMicrosoft (MSRC)
Office Online Server16.0.10417.20097 · KB5002835Microsoft (MSRC)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-78509210 days apartMicrosoft Office Outlook Remote Code Execution Vulnerability
    39Monitor
  • CVE-2026-70242245 days apartMicrosoft Office Outlook Remote Code Execution Vulnerability
    39Monitor
  • CVE-2026-70291245 days apartMicrosoft Office Outlook Remote Code Execution Vulnerability
    39Monitor
  • CVE-2026-97016245 days apartMicrosoft Office Outlook Remote Code Execution Vulnerability
    39Monitor
  • CVE-2026-69629210 days apartMicrosoft Office Outlook Remote Code Execution Vulnerability
    35Monitor
  • CVE-2026-69671210 days apartMicrosoft Office Word Remote Code Execution Vulnerability
    35Monitor

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · public bounty program.

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-122 · Heap-based Buffer Overflow

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records