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Vulnerabilities/CVE-2026-88156Public Intelligence Dossier
Source: Microsoft · Limited verification•Last verified: •Collection Degraded
CVE-2026-88156Unknown / EvaluatingCritical (raw)CVSS 9.8CWE-121

Microsoft Office Outlook Remote Code Execution Vulnerability

Published: 13 Oct 2026•Last updated: 15 Oct 2026, 12:30 PM IST•Source identifier: secure@microsoft.com
Dossier completeness: source-provided sections 3 / 3 · rule guidance available. Missing source facts count as incomplete.
Official source
CISA KEV catalog
Unknown
KEV status was not determined.
CVSS score
9.8Critical (raw)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Metric sourceMicrosoft MSRC CVRF
EPSS probability
1%0.010
Percentile61st
Weakness type
CWE-121
No further CWE recorded
Remediation
Patch status unknown
No fixed version or KB recorded

Why It Matters

Analysis dossier

Why It Matters

Stack-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.

SOC priority

High Severity / Review

Actively exploited

No

Publicly disclosed

Unknown

Risk basis: Microsoft or Microsoft-managed product relevance; CRITICAL severity; Critical CVSS without confirmed KEV exploitation

Affected Products & Remediation

9 source-backed products
Affected products and versions (source)
  • Microsoft Office 365 for Mac · version range not provided by source · Microsoft MSRC · Source
  • Microsoft 365 Apps for Enterprise for 32-bit Systems · version range not provided by source · Microsoft MSRC · Source
  • Microsoft 365 Apps for Enterprise for 64-bit Systems · version range not provided by source · Microsoft MSRC · Source
  • Microsoft Office LTSC for Mac 2021 · version range not provided by source · Microsoft MSRC · Source
  • Microsoft Office LTSC 2021 for 64-bit editions · version range not provided by source · Microsoft MSRC · Source
  • Microsoft Office LTSC 2021 for 32-bit editions · version range not provided by source · Microsoft MSRC · Source
  • Microsoft Office LTSC 2024 for 32-bit editions · version range not provided by source · Microsoft MSRC · Source
  • Microsoft Office LTSC 2024 for 64-bit editions · version range not provided by source · Microsoft MSRC · Source
  • Microsoft Office LTSC for Mac 2024 · version range not provided by source · Microsoft MSRC · Source
Recorded patch / KBNot provided by source

Vendor or catalog guidance (source)

  • Microsoft MSRC: Release Notes

Known exploitation (source facts)

Only what a source states. Unknown means no source has said either way; it is not "not exploited".

CISA KEV
Unknown
Exploited (source statement)
No
Publicly disclosed (source)
Unknown

Suggested hunting (rule-based inference)

SecOps Signal recommendation (rule-based inference). These steps are hunting hypotheses from the vulnerability class; they do not state or imply that exploitation occurred here or anywhere.

Matched network-unauthenticated (CVSS AV:N, CVSS PR:N, CVSS UI:N)

Exposure

  1. Identify devices reporting this CVE and note which expose the affected service to untrusted networks.Telemetry: DeviceTvmSoftwareVulnerabilities · A network-reachable, no-privilege vector makes internet-facing instances the first exposure question. · Rule network-unauthenticated

Exploitation evidence

  1. Review inbound connections to the affected service from unexpected sources since the advisory date.Telemetry: DeviceNetworkEvents · Hunting hypothesis from the CVSS vector; it does not show that exploitation occurred. · Rule network-unauthenticated

Response

  1. Confirm the source-stated update is installed and the CVE is no longer reported.Telemetry: DeviceTvmSoftwareVulnerabilities · A follow-up inventory check verifies remediation. · Rule network-unauthenticated

CISA KEV Record

CISA KEV status was not determined for this record.

Change History & Source Data

— No recorded material change

CNA / source
secure@microsoft.com
Record status · verification
UPDATED · Unknown
CPE
cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x64:*, cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:x86:*, cpe:2.3:a:microsoft:microsoft_365:-:*:*:*:*:macos:*:*, cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x64:*, cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:-:x86:*, cpe:2.3:a:microsoft:office_2021:-:*:*:*:ltsc:macos:-:*, cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x64:*, cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:-:x86:*, cpe:2.3:a:microsoft:office_2024:-:*:*:*:ltsc:macos:-:*

Evidence & Provenance

3 public sources
msrc.microsoft.comSource recordapi.msrc.microsoft.comSource recordnvd.nist.govSource record
Detection Hunting Query

— No published hunting query names this record. Browse community and library queries instead.

Open KQL Library

Correlated briefings

Microsoft Security Update Guide · Limited verificationOctober 2026 Security UpdatesPublished 13 Oct 2026
SecOps Signal surfaces public advisory facts only. A missing value means the source has not published it, not that your environment is unaffected. No tenant inventory is connected.