CVE Intelligence
Medium

CVE-2026-81399 — Microsoft Excel Information Disclosure Vulnerability

Buffer over-read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.

Published Sep 8, 2026 · Updated Oct 15, 2026 · Sources: CVE Program (cve.org) e CISA ADP, NIST National Vulnerability Database · CNA: microsoft

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.5% (30-day exploitation probability)+7
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.54%
ahead of 44% of scored CVEs · Oct 14, 2026
Affects
Microsoft
365 Apps and 13 more
CVSS base
5.5
Medium · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Microsoft 365 Apps, Microsoft Excel, Microsoft Microsoft 365…).
  2. Apply the fixed version or the patch documented under Remediation.
  3. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  4. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Microsoft 365 Apps versions not specified by the source Vulnerable NIST National Vulnerability Database
Microsoft Excel version 2016 Vulnerable NIST National Vulnerability Database
Microsoft Microsoft 365 versions not specified by the source Vulnerable NIST National Vulnerability Database
Microsoft Microsoft 365 Apps for Enterprise ≥ 16.0.1 and < 16.0.20326.20138 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Excel 2016 ≥ 16.0.0.0 and < 16.0.5569.1003 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Office 2016 ≥ 16.0.0 and < 16.0.5569.1003 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Office 2016 versions not specified by the source Vulnerable NIST National Vulnerability Database
Microsoft Microsoft Office 2019 ≥ 19.0.0 and < 16.0.10417.20207 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Office 2019 versions not specified by the source Vulnerable NIST National Vulnerability Database
Microsoft Microsoft Office 365 for Mac ≥ 1.0.0 and < 16.113.26091433 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Office LTSC 2021 ≥ 16.0.1 and < 16.0.14334.20906 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Office LTSC 2024 ≥ 16.0.0 and < 16.0.17932.20976 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Office LTSC for Mac 2021 ≥ 16.0.1 and < 16.113.26091433 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Microsoft Office LTSC for Mac 2024 ≥ 16.0.0 and < 16.113.26091433 Vulnerable CVE Program (cve.org) e CISA ADP
Microsoft Office 2021 versions not specified by the source Vulnerable NIST National Vulnerability Database
Microsoft Office 2024 versions not specified by the source Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
5.5 CVSS 3.1 Medium 1.8 3.6 secure@microsoft.com via NIST National Vulnerability Database
5.5 CVSS 3.1 Medium — — microsoft via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N (score shown at the top: secure@microsoft.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-126

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

  • 2026
  • Fix documented
    Oct 15, 2026 · NIST National Vulnerability Database
  • Affected products added · microsoft/365 apps, microsoft/excel, microsoft/microsoft 365, microsoft/office 2016, microsoft/office 2019, microsoft/of
    Oct 15, 2026 · NIST National Vulnerability Database
  • Source status changed · Published → Analyzed
    Oct 15, 2026 · NIST National Vulnerability Database
  • Record published
    Oct 14, 2026
  • CVSS changed · 5.5
    Oct 14, 2026 · CVE Program (cve.org) e CISA ADP
  • Source status changed · → Published
    Oct 14, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 14, 2026 · CVE Program (cve.org) e CISA ADP
  • Record created in this database
    Oct 14, 2026 · CVE Program (cve.org) e CISA ADP
  • CVE published
    Sep 8, 2026 · microsoft

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 14, 2026 – Oct 14, 2026

References

1 on the record

Elsewhere on this site

Microsoft
every CVE for this vendor
CWE-126
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-108453 Microsoft Office PowerPoint Information Disclosure Vulnerability 2h
  • CVE-2026-108454 Microsoft Office PowerPoint Information Disclosure Vulnerability 2h
  • CVE-2026-108455 Microsoft Office PowerPoint Information Disclosure Vulnerability 2h
  • CVE-2026-108450 Microsoft Office Word Remote Code Execution Vulnerability 2h
  • CVE-2026-108446 Microsoft Office Excel Remote Code Execution Vulnerability 2h
  • CVE-2026-108449 Microsoft Office Word Remote Code Execution Vulnerability 2h

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-81399 is "Microsoft Excel Information Disclosure Vulnerability", rated Medium. It affects 365 Apps (Microsoft); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.5 describes technical severity. EPSS 0.54% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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